Primitive Type str

1.0.0 ·
Expand description

String slices.

See also the std::str module.

The str type, also called a ‘string slice’, is the most primitive string type. It is usually seen in its borrowed form, &str. It is also the type of string literals, &'static str.

String slices are always valid UTF-8.

Basic Usage

String literals are string slices:

let hello_world = "Hello, World!";
Run

Here we have declared a string slice initialized with a string literal. String literals have a static lifetime, which means the string hello_world is guaranteed to be valid for the duration of the entire program. We can explicitly specify hello_world’s lifetime as well:

let hello_world: &'static str = "Hello, world!";
Run

Representation

A &str is made up of two components: a pointer to some bytes, and a length. You can look at these with the as_ptr and len methods:

use std::slice;
use std::str;

let story = "Once upon a time...";

let ptr = story.as_ptr();
let len = story.len();

// story has nineteen bytes
assert_eq!(19, len);

// We can re-build a str out of ptr and len. This is all unsafe because
// we are responsible for making sure the two components are valid:
let s = unsafe {
    // First, we build a &[u8]...
    let slice = slice::from_raw_parts(ptr, len);

    // ... and then convert that slice into a string slice
    str::from_utf8(slice)
};

assert_eq!(s, Ok(story));
Run

Note: This example shows the internals of &str. unsafe should not be used to get a string slice under normal circumstances. Use as_str instead.

Implementations§

source§

impl str

const: 1.39.0 · source

pub const fn len(&self) -> usize

Returns the length of self.

This length is in bytes, not chars or graphemes. In other words, it might not be what a human considers the length of the string.

Examples

Basic usage:

let len = "foo".len();
assert_eq!(3, len);

assert_eq!("ƒoo".len(), 4); // fancy f!
assert_eq!("ƒoo".chars().count(), 3);
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const: 1.39.0 · source

pub const fn is_empty(&self) -> bool

Returns true if self has a length of zero bytes.

Examples

Basic usage:

let s = "";
assert!(s.is_empty());

let s = "not empty";
assert!(!s.is_empty());
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1.9.0 (const: unstable) · source

pub fn is_char_boundary(&self, index: usize) -> bool

Checks that index-th byte is the first byte in a UTF-8 code point sequence or the end of the string.

The start and end of the string (when index == self.len()) are considered to be boundaries.

Returns false if index is greater than self.len().

Examples
let s = "Löwe 老虎 Léopard";
assert!(s.is_char_boundary(0));
// start of `老`
assert!(s.is_char_boundary(6));
assert!(s.is_char_boundary(s.len()));

// second byte of `ö`
assert!(!s.is_char_boundary(2));

// third byte of `老`
assert!(!s.is_char_boundary(8));
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source

pub fn floor_char_boundary(&self, index: usize) -> usize

🔬This is a nightly-only experimental API. (round_char_boundary #93743)

Finds the closest x not exceeding index where is_char_boundary(x) is true.

This method can help you truncate a string so that it’s still valid UTF-8, but doesn’t exceed a given number of bytes. Note that this is done purely at the character level and can still visually split graphemes, even though the underlying characters aren’t split. For example, the emoji 🧑‍🔬 (scientist) could be split so that the string only includes 🧑 (person) instead.

Examples
#![feature(round_char_boundary)]
let s = "❤️🧡💛💚💙💜";
assert_eq!(s.len(), 26);
assert!(!s.is_char_boundary(13));

let closest = s.floor_char_boundary(13);
assert_eq!(closest, 10);
assert_eq!(&s[..closest], "❤️🧡");
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source

pub fn ceil_char_boundary(&self, index: usize) -> usize

🔬This is a nightly-only experimental API. (round_char_boundary #93743)

Finds the closest x not below index where is_char_boundary(x) is true.

This method is the natural complement to floor_char_boundary. See that method for more details.

Panics

Panics if index > self.len().

Examples
#![feature(round_char_boundary)]
let s = "❤️🧡💛💚💙💜";
assert_eq!(s.len(), 26);
assert!(!s.is_char_boundary(13));

let closest = s.ceil_char_boundary(13);
assert_eq!(closest, 14);
assert_eq!(&s[..closest], "❤️🧡💛");
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const: 1.39.0 · source

pub const fn as_bytes(&self) -> &[u8]

Converts a string slice to a byte slice. To convert the byte slice back into a string slice, use the from_utf8 function.

Examples

Basic usage:

let bytes = "bors".as_bytes();
assert_eq!(b"bors", bytes);
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1.20.0 · source

pub unsafe fn as_bytes_mut(&mut self) -> &mut [u8]

Converts a mutable string slice to a mutable byte slice.

Safety

The caller must ensure that the content of the slice is valid UTF-8 before the borrow ends and the underlying str is used.

Use of a str whose contents are not valid UTF-8 is undefined behavior.

Examples

Basic usage:

let mut s = String::from("Hello");
let bytes = unsafe { s.as_bytes_mut() };

assert_eq!(b"Hello", bytes);
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Mutability:

let mut s = String::from("🗻∈🌏");

unsafe {
    let bytes = s.as_bytes_mut();

    bytes[0] = 0xF0;
    bytes[1] = 0x9F;
    bytes[2] = 0x8D;
    bytes[3] = 0x94;
}

assert_eq!("🍔∈🌏", s);
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const: 1.32.0 · source

pub const fn as_ptr(&self) -> *const u8

Converts a string slice to a raw pointer.

As string slices are a slice of bytes, the raw pointer points to a u8. This pointer will be pointing to the first byte of the string slice.

The caller must ensure that the returned pointer is never written to. If you need to mutate the contents of the string slice, use as_mut_ptr.

Examples

Basic usage:

let s = "Hello";
let ptr = s.as_ptr();
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1.36.0 · source

pub fn as_mut_ptr(&mut self) -> *mut u8

Converts a mutable string slice to a raw pointer.

As string slices are a slice of bytes, the raw pointer points to a u8. This pointer will be pointing to the first byte of the string slice.

It is your responsibility to make sure that the string slice only gets modified in a way that it remains valid UTF-8.

1.20.0 (const: unstable) · source

pub fn get<I>(&self, i: I) -> Option<&<I as SliceIndex<str>>::Output>where
    I: SliceIndex<str>,

Returns a subslice of str.

This is the non-panicking alternative to indexing the str. Returns None whenever equivalent indexing operation would panic.

Examples
let v = String::from("🗻∈🌏");

assert_eq!(Some("🗻"), v.get(0..4));

// indices not on UTF-8 sequence boundaries
assert!(v.get(1..).is_none());
assert!(v.get(..8).is_none());

// out of bounds
assert!(v.get(..42).is_none());
Run
1.20.0 (const: unstable) · source

pub fn get_mut<I>(&mut self, i: I) -> Option<&mut <I as SliceIndex<str>>::Output>where
    I: SliceIndex<str>,

Returns a mutable subslice of str.

This is the non-panicking alternative to indexing the str. Returns None whenever equivalent indexing operation would panic.

Examples
let mut v = String::from("hello");
// correct length
assert!(v.get_mut(0..5).is_some());
// out of bounds
assert!(v.get_mut(..42).is_none());
assert_eq!(Some("he"), v.get_mut(0..2).map(|v| &*v));

assert_eq!("hello", v);
{
    let s = v.get_mut(0..2);
    let s = s.map(|s| {
        s.make_ascii_uppercase();
        &*s
    });
    assert_eq!(Some("HE"), s);
}
assert_eq!("HEllo", v);
Run
1.20.0 (const: unstable) · source

pub unsafe fn get_unchecked<I>(&self, i: I) -> &<I as SliceIndex<str>>::Outputwhere
    I: SliceIndex<str>,

Returns an unchecked subslice of str.

This is the unchecked alternative to indexing the str.

Safety

Callers of this function are responsible that these preconditions are satisfied:

  • The starting index must not exceed the ending index;
  • Indexes must be within bounds of the original slice;
  • Indexes must lie on UTF-8 sequence boundaries.

Failing that, the returned string slice may reference invalid memory or violate the invariants communicated by the str type.

Examples
let v = "🗻∈🌏";
unsafe {
    assert_eq!("🗻", v.get_unchecked(0..4));
    assert_eq!("∈", v.get_unchecked(4..7));
    assert_eq!("🌏", v.get_unchecked(7..11));
}
Run
1.20.0 (const: unstable) · source

pub unsafe fn get_unchecked_mut<I>(
    &mut self,
    i: I
) -> &mut <I as SliceIndex<str>>::Outputwhere
    I: SliceIndex<str>,

Returns a mutable, unchecked subslice of str.

This is the unchecked alternative to indexing the str.

Safety

Callers of this function are responsible that these preconditions are satisfied:

  • The starting index must not exceed the ending index;
  • Indexes must be within bounds of the original slice;
  • Indexes must lie on UTF-8 sequence boundaries.

Failing that, the returned string slice may reference invalid memory or violate the invariants communicated by the str type.

Examples
let mut v = String::from("🗻∈🌏");
unsafe {
    assert_eq!("🗻", v.get_unchecked_mut(0..4));
    assert_eq!("∈", v.get_unchecked_mut(4..7));
    assert_eq!("🌏", v.get_unchecked_mut(7..11));
}
Run
source

pub unsafe fn slice_unchecked(&self, begin: usize, end: usize) -> &str

👎Deprecated since 1.29.0: use get_unchecked(begin..end) instead

Creates a string slice from another string slice, bypassing safety checks.

This is generally not recommended, use with caution! For a safe alternative see str and Index.

This new slice goes from begin to end, including begin but excluding end.

To get a mutable string slice instead, see the slice_mut_unchecked method.

Safety

Callers of this function are responsible that three preconditions are satisfied:

  • begin must not exceed end.
  • begin and end must be byte positions within the string slice.
  • begin and end must lie on UTF-8 sequence boundaries.
Examples

Basic usage:

let s = "Löwe 老虎 Léopard";

unsafe {
    assert_eq!("Löwe 老虎 Léopard", s.slice_unchecked(0, 21));
}

let s = "Hello, world!";

unsafe {
    assert_eq!("world", s.slice_unchecked(7, 12));
}
Run
1.5.0 · source

pub unsafe fn slice_mut_unchecked(&mut self, begin: usize, end: usize) -> &mut str

👎Deprecated since 1.29.0: use get_unchecked_mut(begin..end) instead

Creates a string slice from another string slice, bypassing safety checks. This is generally not recommended, use with caution! For a safe alternative see str and IndexMut.

This new slice goes from begin to end, including begin but excluding end.

To get an immutable string slice instead, see the slice_unchecked method.

Safety

Callers of this function are responsible that three preconditions are satisfied:

  • begin must not exceed end.
  • begin and end must be byte positions within the string slice.
  • begin and end must lie on UTF-8 sequence boundaries.
1.4.0 · source

pub fn split_at(&self, mid: usize) -> (&str, &str)

Divide one string slice into two at an index.

The argument, mid, should be a byte offset from the start of the string. It must also be on the boundary of a UTF-8 code point.

The two slices returned go from the start of the string slice to mid, and from mid to the end of the string slice.

To get mutable string slices instead, see the split_at_mut method.

Panics

Panics if mid is not on a UTF-8 code point boundary, or if it is past the end of the last code point of the string slice.

Examples

Basic usage:

let s = "Per Martin-Löf";

let (first, last) = s.split_at(3);

assert_eq!("Per", first);
assert_eq!(" Martin-Löf", last);
Run
1.4.0 · source

pub fn split_at_mut(&mut self, mid: usize) -> (&mut str, &mut str)

Divide one mutable string slice into two at an index.

The argument, mid, should be a byte offset from the start of the string. It must also be on the boundary of a UTF-8 code point.

The two slices returned go from the start of the string slice to mid, and from mid to the end of the string slice.

To get immutable string slices instead, see the split_at method.

Panics

Panics if mid is not on a UTF-8 code point boundary, or if it is past the end of the last code point of the string slice.

Examples

Basic usage:

let mut s = "Per Martin-Löf".to_string();
{
    let (first, last) = s.split_at_mut(3);
    first.make_ascii_uppercase();
    assert_eq!("PER", first);
    assert_eq!(" Martin-Löf", last);
}
assert_eq!("PER Martin-Löf", s);
Run
source

pub fn chars(&self) -> Chars<'_>

Returns an iterator over the chars of a string slice.

As a string slice consists of valid UTF-8, we can iterate through a string slice by char. This method returns such an iterator.

It’s important to remember that char represents a Unicode Scalar Value, and might not match your idea of what a ‘character’ is. Iteration over grapheme clusters may be what you actually want. This functionality is not provided by Rust’s standard library, check crates.io instead.

Examples

Basic usage:

let word = "goodbye";

let count = word.chars().count();
assert_eq!(7, count);

let mut chars = word.chars();

assert_eq!(Some('g'), chars.next());
assert_eq!(Some('o'), chars.next());
assert_eq!(Some('o'), chars.next());
assert_eq!(Some('d'), chars.next());
assert_eq!(Some('b'), chars.next());
assert_eq!(Some('y'), chars.next());
assert_eq!(Some('e'), chars.next());

assert_eq!(None, chars.next());
Run

Remember, chars might not match your intuition about characters:

let y = "y̆";

let mut chars = y.chars();

assert_eq!(Some('y'), chars.next()); // not 'y̆'
assert_eq!(Some('\u{0306}'), chars.next());

assert_eq!(None, chars.next());
Run
source

pub fn char_indices(&self) -> CharIndices<'_>

Returns an iterator over the chars of a string slice, and their positions.

As a string slice consists of valid UTF-8, we can iterate through a string slice by char. This method returns an iterator of both these chars, as well as their byte positions.

The iterator yields tuples. The position is first, the char is second.

Examples

Basic usage:

let word = "goodbye";

let count = word.char_indices().count();
assert_eq!(7, count);

let mut char_indices = word.char_indices();

assert_eq!(Some((0, 'g')), char_indices.next());
assert_eq!(Some((1, 'o')), char_indices.next());
assert_eq!(Some((2, 'o')), char_indices.next());
assert_eq!(Some((3, 'd')), char_indices.next());
assert_eq!(Some((4, 'b')), char_indices.next());
assert_eq!(Some((5, 'y')), char_indices.next());
assert_eq!(Some((6, 'e')), char_indices.next());

assert_eq!(None, char_indices.next());
Run

Remember, chars might not match your intuition about characters:

let yes = "y̆es";

let mut char_indices = yes.char_indices();

assert_eq!(Some((0, 'y')), char_indices.next()); // not (0, 'y̆')
assert_eq!(Some((1, '\u{0306}')), char_indices.next());

// note the 3 here - the last character took up two bytes
assert_eq!(Some((3, 'e')), char_indices.next());
assert_eq!(Some((4, 's')), char_indices.next());

assert_eq!(None, char_indices.next());
Run
source

pub fn bytes(&self) -> Bytes<'_>

An iterator over the bytes of a string slice.

As a string slice consists of a sequence of bytes, we can iterate through a string slice by byte. This method returns such an iterator.

Examples

Basic usage:

let mut bytes = "bors".bytes();

assert_eq!(Some(b'b'), bytes.next());
assert_eq!(Some(b'o'), bytes.next());
assert_eq!(Some(b'r'), bytes.next());
assert_eq!(Some(b's'), bytes.next());

assert_eq!(None, bytes.next());
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1.1.0 · source

pub fn split_whitespace(&self) -> SplitWhitespace<'_>

Splits a string slice by whitespace.

The iterator returned will return string slices that are sub-slices of the original string slice, separated by any amount of whitespace.

‘Whitespace’ is defined according to the terms of the Unicode Derived Core Property White_Space. If you only want to split on ASCII whitespace instead, use split_ascii_whitespace.

Examples

Basic usage:

let mut iter = "A few words".split_whitespace();

assert_eq!(Some("A"), iter.next());
assert_eq!(Some("few"), iter.next());
assert_eq!(Some("words"), iter.next());

assert_eq!(None, iter.next());
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All kinds of whitespace are considered:

let mut iter = " Mary   had\ta\u{2009}little  \n\t lamb".split_whitespace();
assert_eq!(Some("Mary"), iter.next());
assert_eq!(Some("had"), iter.next());
assert_eq!(Some("a"), iter.next());
assert_eq!(Some("little"), iter.next());
assert_eq!(Some("lamb"), iter.next());

assert_eq!(None, iter.next());
Run

If the string is empty or all whitespace, the iterator yields no string slices:

assert_eq!("".split_whitespace().next(), None);
assert_eq!("   ".split_whitespace().next(), None);
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1.34.0 · source

pub fn split_ascii_whitespace(&self) -> SplitAsciiWhitespace<'_>

Splits a string slice by ASCII whitespace.

The iterator returned will return string slices that are sub-slices of the original string slice, separated by any amount of ASCII whitespace.

To split by Unicode Whitespace instead, use split_whitespace.

Examples

Basic usage:

let mut iter = "A few words".split_ascii_whitespace();

assert_eq!(Some("A"), iter.next());
assert_eq!(Some("few"), iter.next());
assert_eq!(Some("words"), iter.next());

assert_eq!(None, iter.next());
Run

All kinds of ASCII whitespace are considered:

let mut iter = " Mary   had\ta little  \n\t lamb".split_ascii_whitespace();
assert_eq!(Some("Mary"), iter.next());
assert_eq!(Some("had"), iter.next());
assert_eq!(Some("a"), iter.next());
assert_eq!(Some("little"), iter.next());
assert_eq!(Some("lamb"), iter.next());

assert_eq!(None, iter.next());
Run

If the string is empty or all ASCII whitespace, the iterator yields no string slices:

assert_eq!("".split_ascii_whitespace().next(), None);
assert_eq!("   ".split_ascii_whitespace().next(), None);
Run
source

pub fn lines(&self) -> Lines<'_>

An iterator over the lines of a string, as string slices.

Lines are split at line endings that are either newlines (\n) or sequences of a carriage return followed by a line feed (\r\n).

Line terminators are not included in the lines returned by the iterator.

The final line ending is optional. A string that ends with a final line ending will return the same lines as an otherwise identical string without a final line ending.

Examples

Basic usage:

let text = "foo\r\nbar\n\nbaz\n";
let mut lines = text.lines();

assert_eq!(Some("foo"), lines.next());
assert_eq!(Some("bar"), lines.next());
assert_eq!(Some(""), lines.next());
assert_eq!(Some("baz"), lines.next());

assert_eq!(None, lines.next());
Run

The final line ending isn’t required:

let text = "foo\nbar\n\r\nbaz";
let mut lines = text.lines();

assert_eq!(Some("foo"), lines.next());
assert_eq!(Some("bar"), lines.next());
assert_eq!(Some(""), lines.next());
assert_eq!(Some("baz"), lines.next());

assert_eq!(None, lines.next());
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source

pub fn lines_any(&self) -> LinesAny<'_>

👎Deprecated since 1.4.0: use lines() instead now

An iterator over the lines of a string.

1.8.0 · source

pub fn encode_utf16(&self) -> EncodeUtf16<'_>

Returns an iterator of u16 over the string encoded as UTF-16.

Examples

Basic usage:

let text = "Zażółć gęślą jaźń";

let utf8_len = text.len();
let utf16_len = text.encode_utf16().count();

assert!(utf16_len <= utf8_len);
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source

pub fn contains<'a, P>(&'a self, pat: P) -> boolwhere
    P: Pattern<'a>,

Returns true if the given pattern matches a sub-slice of this string slice.

Returns false if it does not.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Examples

Basic usage:

let bananas = "bananas";

assert!(bananas.contains("nana"));
assert!(!bananas.contains("apples"));
Run
source

pub fn starts_with<'a, P>(&'a self, pat: P) -> boolwhere
    P: Pattern<'a>,

Returns true if the given pattern matches a prefix of this string slice.

Returns false if it does not.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Examples

Basic usage:

let bananas = "bananas";

assert!(bananas.starts_with("bana"));
assert!(!bananas.starts_with("nana"));
Run
source

pub fn ends_with<'a, P>(&'a self, pat: P) -> boolwhere
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,

Returns true if the given pattern matches a suffix of this string slice.

Returns false if it does not.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Examples

Basic usage:

let bananas = "bananas";

assert!(bananas.ends_with("anas"));
assert!(!bananas.ends_with("nana"));
Run
source

pub fn find<'a, P>(&'a self, pat: P) -> Option<usize>where
    P: Pattern<'a>,

Returns the byte index of the first character of this string slice that matches the pattern.

Returns None if the pattern doesn’t match.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Examples

Simple patterns:

let s = "Löwe 老虎 Léopard Gepardi";

assert_eq!(s.find('L'), Some(0));
assert_eq!(s.find('é'), Some(14));
assert_eq!(s.find("pard"), Some(17));
Run

More complex patterns using point-free style and closures:

let s = "Löwe 老虎 Léopard";

assert_eq!(s.find(char::is_whitespace), Some(5));
assert_eq!(s.find(char::is_lowercase), Some(1));
assert_eq!(s.find(|c: char| c.is_whitespace() || c.is_lowercase()), Some(1));
assert_eq!(s.find(|c: char| (c < 'o') && (c > 'a')), Some(4));
Run

Not finding the pattern:

let s = "Löwe 老虎 Léopard";
let x: &[_] = &['1', '2'];

assert_eq!(s.find(x), None);
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source

pub fn rfind<'a, P>(&'a self, pat: P) -> Option<usize>where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,

Returns the byte index for the first character of the last match of the pattern in this string slice.

Returns None if the pattern doesn’t match.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Examples

Simple patterns:

let s = "Löwe 老虎 Léopard Gepardi";

assert_eq!(s.rfind('L'), Some(13));
assert_eq!(s.rfind('é'), Some(14));
assert_eq!(s.rfind("pard"), Some(24));
Run

More complex patterns with closures:

let s = "Löwe 老虎 Léopard";

assert_eq!(s.rfind(char::is_whitespace), Some(12));
assert_eq!(s.rfind(char::is_lowercase), Some(20));
Run

Not finding the pattern:

let s = "Löwe 老虎 Léopard";
let x: &[_] = &['1', '2'];

assert_eq!(s.rfind(x), None);
Run
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pub fn split<'a, P>(&'a self, pat: P) -> Split<'a, P> where
    P: Pattern<'a>,

An iterator over substrings of this string slice, separated by characters matched by a pattern.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Iterator behavior

The returned iterator will be a DoubleEndedIterator if the pattern allows a reverse search and forward/reverse search yields the same elements. This is true for, e.g., char, but not for &str.

If the pattern allows a reverse search but its results might differ from a forward search, the rsplit method can be used.

Examples

Simple patterns:

let v: Vec<&str> = "Mary had a little lamb".split(' ').collect();
assert_eq!(v, ["Mary", "had", "a", "little", "lamb"]);

let v: Vec<&str> = "".split('X').collect();
assert_eq!(v, [""]);

let v: Vec<&str> = "lionXXtigerXleopard".split('X').collect();
assert_eq!(v, ["lion", "", "tiger", "leopard"]);

let v: Vec<&str> = "lion::tiger::leopard".split("::").collect();
assert_eq!(v, ["lion", "tiger", "leopard"]);

let v: Vec<&str> = "abc1def2ghi".split(char::is_numeric).collect();
assert_eq!(v, ["abc", "def", "ghi"]);

let v: Vec<&str> = "lionXtigerXleopard".split(char::is_uppercase).collect();
assert_eq!(v, ["lion", "tiger", "leopard"]);
Run

If the pattern is a slice of chars, split on each occurrence of any of the characters:

let v: Vec<&str> = "2020-11-03 23:59".split(&['-', ' ', ':', '@'][..]).collect();
assert_eq!(v, ["2020", "11", "03", "23", "59"]);
Run

A more complex pattern, using a closure:

let v: Vec<&str> = "abc1defXghi".split(|c| c == '1' || c == 'X').collect();
assert_eq!(v, ["abc", "def", "ghi"]);
Run

If a string contains multiple contiguous separators, you will end up with empty strings in the output:

let x = "||||a||b|c".to_string();
let d: Vec<_> = x.split('|').collect();

assert_eq!(d, &["", "", "", "", "a", "", "b", "c"]);
Run

Contiguous separators are separated by the empty string.

let x = "(///)".to_string();
let d: Vec<_> = x.split('/').collect();

assert_eq!(d, &["(", "", "", ")"]);
Run

Separators at the start or end of a string are neighbored by empty strings.

let d: Vec<_> = "010".split("0").collect();
assert_eq!(d, &["", "1", ""]);
Run

When the empty string is used as a separator, it separates every character in the string, along with the beginning and end of the string.

let f: Vec<_> = "rust".split("").collect();
assert_eq!(f, &["", "r", "u", "s", "t", ""]);
Run

Contiguous separators can lead to possibly surprising behavior when whitespace is used as the separator. This code is correct:

let x = "    a  b c".to_string();
let d: Vec<_> = x.split(' ').collect();

assert_eq!(d, &["", "", "", "", "a", "", "b", "c"]);
Run

It does not give you:

assert_eq!(d, &["a", "b", "c"]);
Run

Use split_whitespace for this behavior.

1.51.0 · source

pub fn split_inclusive<'a, P>(&'a self, pat: P) -> SplitInclusive<'a, P> where
    P: Pattern<'a>,

An iterator over substrings of this string slice, separated by characters matched by a pattern. Differs from the iterator produced by split in that split_inclusive leaves the matched part as the terminator of the substring.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Examples
let v: Vec<&str> = "Mary had a little lamb\nlittle lamb\nlittle lamb."
    .split_inclusive('\n').collect();
assert_eq!(v, ["Mary had a little lamb\n", "little lamb\n", "little lamb."]);
Run

If the last element of the string is matched, that element will be considered the terminator of the preceding substring. That substring will be the last item returned by the iterator.

let v: Vec<&str> = "Mary had a little lamb\nlittle lamb\nlittle lamb.\n"
    .split_inclusive('\n').collect();
assert_eq!(v, ["Mary had a little lamb\n", "little lamb\n", "little lamb.\n"]);
Run
source

pub fn rsplit<'a, P>(&'a self, pat: P) -> RSplit<'a, P> where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,

An iterator over substrings of the given string slice, separated by characters matched by a pattern and yielded in reverse order.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Iterator behavior

The returned iterator requires that the pattern supports a reverse search, and it will be a DoubleEndedIterator if a forward/reverse search yields the same elements.

For iterating from the front, the split method can be used.

Examples

Simple patterns:

let v: Vec<&str> = "Mary had a little lamb".rsplit(' ').collect();
assert_eq!(v, ["lamb", "little", "a", "had", "Mary"]);

let v: Vec<&str> = "".rsplit('X').collect();
assert_eq!(v, [""]);

let v: Vec<&str> = "lionXXtigerXleopard".rsplit('X').collect();
assert_eq!(v, ["leopard", "tiger", "", "lion"]);

let v: Vec<&str> = "lion::tiger::leopard".rsplit("::").collect();
assert_eq!(v, ["leopard", "tiger", "lion"]);
Run

A more complex pattern, using a closure:

let v: Vec<&str> = "abc1defXghi".rsplit(|c| c == '1' || c == 'X').collect();
assert_eq!(v, ["ghi", "def", "abc"]);
Run
source

pub fn split_terminator<'a, P>(&'a self, pat: P) -> SplitTerminator<'a, P> where
    P: Pattern<'a>,

An iterator over substrings of the given string slice, separated by characters matched by a pattern.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Equivalent to split, except that the trailing substring is skipped if empty.

This method can be used for string data that is terminated, rather than separated by a pattern.

Iterator behavior

The returned iterator will be a DoubleEndedIterator if the pattern allows a reverse search and forward/reverse search yields the same elements. This is true for, e.g., char, but not for &str.

If the pattern allows a reverse search but its results might differ from a forward search, the rsplit_terminator method can be used.

Examples

Basic usage:

let v: Vec<&str> = "A.B.".split_terminator('.').collect();
assert_eq!(v, ["A", "B"]);

let v: Vec<&str> = "A..B..".split_terminator(".").collect();
assert_eq!(v, ["A", "", "B", ""]);

let v: Vec<&str> = "A.B:C.D".split_terminator(&['.', ':'][..]).collect();
assert_eq!(v, ["A", "B", "C", "D"]);
Run
source

pub fn rsplit_terminator<'a, P>(&'a self, pat: P) -> RSplitTerminator<'a, P> where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,

An iterator over substrings of self, separated by characters matched by a pattern and yielded in reverse order.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Equivalent to split, except that the trailing substring is skipped if empty.

This method can be used for string data that is terminated, rather than separated by a pattern.

Iterator behavior

The returned iterator requires that the pattern supports a reverse search, and it will be double ended if a forward/reverse search yields the same elements.

For iterating from the front, the split_terminator method can be used.

Examples
let v: Vec<&str> = "A.B.".rsplit_terminator('.').collect();
assert_eq!(v, ["B", "A"]);

let v: Vec<&str> = "A..B..".rsplit_terminator(".").collect();
assert_eq!(v, ["", "B", "", "A"]);

let v: Vec<&str> = "A.B:C.D".rsplit_terminator(&['.', ':'][..]).collect();
assert_eq!(v, ["D", "C", "B", "A"]);
Run
source

pub fn splitn<'a, P>(&'a self, n: usize, pat: P) -> SplitN<'a, P> where
    P: Pattern<'a>,

An iterator over substrings of the given string slice, separated by a pattern, restricted to returning at most n items.

If n substrings are returned, the last substring (the nth substring) will contain the remainder of the string.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Iterator behavior

The returned iterator will not be double ended, because it is not efficient to support.

If the pattern allows a reverse search, the rsplitn method can be used.

Examples

Simple patterns:

let v: Vec<&str> = "Mary had a little lambda".splitn(3, ' ').collect();
assert_eq!(v, ["Mary", "had", "a little lambda"]);

let v: Vec<&str> = "lionXXtigerXleopard".splitn(3, "X").collect();
assert_eq!(v, ["lion", "", "tigerXleopard"]);

let v: Vec<&str> = "abcXdef".splitn(1, 'X').collect();
assert_eq!(v, ["abcXdef"]);

let v: Vec<&str> = "".splitn(1, 'X').collect();
assert_eq!(v, [""]);
Run

A more complex pattern, using a closure:

let v: Vec<&str> = "abc1defXghi".splitn(2, |c| c == '1' || c == 'X').collect();
assert_eq!(v, ["abc", "defXghi"]);
Run
source

pub fn rsplitn<'a, P>(&'a self, n: usize, pat: P) -> RSplitN<'a, P> where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,

An iterator over substrings of this string slice, separated by a pattern, starting from the end of the string, restricted to returning at most n items.

If n substrings are returned, the last substring (the nth substring) will contain the remainder of the string.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Iterator behavior

The returned iterator will not be double ended, because it is not efficient to support.

For splitting from the front, the splitn method can be used.

Examples

Simple patterns:

let v: Vec<&str> = "Mary had a little lamb".rsplitn(3, ' ').collect();
assert_eq!(v, ["lamb", "little", "Mary had a"]);

let v: Vec<&str> = "lionXXtigerXleopard".rsplitn(3, 'X').collect();
assert_eq!(v, ["leopard", "tiger", "lionX"]);

let v: Vec<&str> = "lion::tiger::leopard".rsplitn(2, "::").collect();
assert_eq!(v, ["leopard", "lion::tiger"]);
Run

A more complex pattern, using a closure:

let v: Vec<&str> = "abc1defXghi".rsplitn(2, |c| c == '1' || c == 'X').collect();
assert_eq!(v, ["ghi", "abc1def"]);
Run
1.52.0 · source

pub fn split_once<'a, P>(&'a self, delimiter: P) -> Option<(&'a str, &'a str)>where
    P: Pattern<'a>,

Splits the string on the first occurrence of the specified delimiter and returns prefix before delimiter and suffix after delimiter.

Examples
assert_eq!("cfg".split_once('='), None);
assert_eq!("cfg=".split_once('='), Some(("cfg", "")));
assert_eq!("cfg=foo".split_once('='), Some(("cfg", "foo")));
assert_eq!("cfg=foo=bar".split_once('='), Some(("cfg", "foo=bar")));
Run
1.52.0 · source

pub fn rsplit_once<'a, P>(&'a self, delimiter: P) -> Option<(&'a str, &'a str)>where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,

Splits the string on the last occurrence of the specified delimiter and returns prefix before delimiter and suffix after delimiter.

Examples
assert_eq!("cfg".rsplit_once('='), None);
assert_eq!("cfg=foo".rsplit_once('='), Some(("cfg", "foo")));
assert_eq!("cfg=foo=bar".rsplit_once('='), Some(("cfg=foo", "bar")));
Run
1.2.0 · source

pub fn matches<'a, P>(&'a self, pat: P) -> Matches<'a, P> where
    P: Pattern<'a>,

An iterator over the disjoint matches of a pattern within the given string slice.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Iterator behavior

The returned iterator will be a DoubleEndedIterator if the pattern allows a reverse search and forward/reverse search yields the same elements. This is true for, e.g., char, but not for &str.

If the pattern allows a reverse search but its results might differ from a forward search, the rmatches method can be used.

Examples

Basic usage:

let v: Vec<&str> = "abcXXXabcYYYabc".matches("abc").collect();
assert_eq!(v, ["abc", "abc", "abc"]);

let v: Vec<&str> = "1abc2abc3".matches(char::is_numeric).collect();
assert_eq!(v, ["1", "2", "3"]);
Run
1.2.0 · source

pub fn rmatches<'a, P>(&'a self, pat: P) -> RMatches<'a, P> where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,

An iterator over the disjoint matches of a pattern within this string slice, yielded in reverse order.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Iterator behavior

The returned iterator requires that the pattern supports a reverse search, and it will be a DoubleEndedIterator if a forward/reverse search yields the same elements.

For iterating from the front, the matches method can be used.

Examples

Basic usage:

let v: Vec<&str> = "abcXXXabcYYYabc".rmatches("abc").collect();
assert_eq!(v, ["abc", "abc", "abc"]);

let v: Vec<&str> = "1abc2abc3".rmatches(char::is_numeric).collect();
assert_eq!(v, ["3", "2", "1"]);
Run
1.5.0 · source

pub fn match_indices<'a, P>(&'a self, pat: P) -> MatchIndices<'a, P> where
    P: Pattern<'a>,

An iterator over the disjoint matches of a pattern within this string slice as well as the index that the match starts at.

For matches of pat within self that overlap, only the indices corresponding to the first match are returned.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Iterator behavior

The returned iterator will be a DoubleEndedIterator if the pattern allows a reverse search and forward/reverse search yields the same elements. This is true for, e.g., char, but not for &str.

If the pattern allows a reverse search but its results might differ from a forward search, the rmatch_indices method can be used.

Examples

Basic usage:

let v: Vec<_> = "abcXXXabcYYYabc".match_indices("abc").collect();
assert_eq!(v, [(0, "abc"), (6, "abc"), (12, "abc")]);

let v: Vec<_> = "1abcabc2".match_indices("abc").collect();
assert_eq!(v, [(1, "abc"), (4, "abc")]);

let v: Vec<_> = "ababa".match_indices("aba").collect();
assert_eq!(v, [(0, "aba")]); // only the first `aba`
Run
1.5.0 · source

pub fn rmatch_indices<'a, P>(&'a self, pat: P) -> RMatchIndices<'a, P> where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,

An iterator over the disjoint matches of a pattern within self, yielded in reverse order along with the index of the match.

For matches of pat within self that overlap, only the indices corresponding to the last match are returned.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Iterator behavior

The returned iterator requires that the pattern supports a reverse search, and it will be a DoubleEndedIterator if a forward/reverse search yields the same elements.

For iterating from the front, the match_indices method can be used.

Examples

Basic usage:

let v: Vec<_> = "abcXXXabcYYYabc".rmatch_indices("abc").collect();
assert_eq!(v, [(12, "abc"), (6, "abc"), (0, "abc")]);

let v: Vec<_> = "1abcabc2".rmatch_indices("abc").collect();
assert_eq!(v, [(4, "abc"), (1, "abc")]);

let v: Vec<_> = "ababa".rmatch_indices("aba").collect();
assert_eq!(v, [(2, "aba")]); // only the last `aba`
Run
source

pub fn trim(&self) -> &str

Returns a string slice with leading and trailing whitespace removed.

‘Whitespace’ is defined according to the terms of the Unicode Derived Core Property White_Space, which includes newlines.

Examples

Basic usage:

let s = "\n Hello\tworld\t\n";

assert_eq!("Hello\tworld", s.trim());
Run
1.30.0 · source

pub fn trim_start(&self) -> &str

Returns a string slice with leading whitespace removed.

‘Whitespace’ is defined according to the terms of the Unicode Derived Core Property White_Space, which includes newlines.

Text directionality

A string is a sequence of bytes. start in this context means the first position of that byte string; for a left-to-right language like English or Russian, this will be left side, and for right-to-left languages like Arabic or Hebrew, this will be the right side.

Examples

Basic usage:

let s = "\n Hello\tworld\t\n";
assert_eq!("Hello\tworld\t\n", s.trim_start());
Run

Directionality:

let s = "  English  ";
assert!(Some('E') == s.trim_start().chars().next());

let s = "  עברית  ";
assert!(Some('ע') == s.trim_start().chars().next());
Run
1.30.0 · source

pub fn trim_end(&self) -> &str

Returns a string slice with trailing whitespace removed.

‘Whitespace’ is defined according to the terms of the Unicode Derived Core Property White_Space, which includes newlines.

Text directionality

A string is a sequence of bytes. end in this context means the last position of that byte string; for a left-to-right language like English or Russian, this will be right side, and for right-to-left languages like Arabic or Hebrew, this will be the left side.

Examples

Basic usage:

let s = "\n Hello\tworld\t\n";
assert_eq!("\n Hello\tworld", s.trim_end());
Run

Directionality:

let s = "  English  ";
assert!(Some('h') == s.trim_end().chars().rev().next());

let s = "  עברית  ";
assert!(Some('ת') == s.trim_end().chars().rev().next());
Run
source

pub fn trim_left(&self) -> &str

👎Deprecated since 1.33.0: superseded by trim_start

Returns a string slice with leading whitespace removed.

‘Whitespace’ is defined according to the terms of the Unicode Derived Core Property White_Space.

Text directionality

A string is a sequence of bytes. ‘Left’ in this context means the first position of that byte string; for a language like Arabic or Hebrew which are ‘right to left’ rather than ‘left to right’, this will be the right side, not the left.

Examples

Basic usage:

let s = " Hello\tworld\t";

assert_eq!("Hello\tworld\t", s.trim_left());
Run

Directionality:

let s = "  English";
assert!(Some('E') == s.trim_left().chars().next());

let s = "  עברית";
assert!(Some('ע') == s.trim_left().chars().next());
Run
source

pub fn trim_right(&self) -> &str

👎Deprecated since 1.33.0: superseded by trim_end

Returns a string slice with trailing whitespace removed.

‘Whitespace’ is defined according to the terms of the Unicode Derived Core Property White_Space.

Text directionality

A string is a sequence of bytes. ‘Right’ in this context means the last position of that byte string; for a language like Arabic or Hebrew which are ‘right to left’ rather than ‘left to right’, this will be the left side, not the right.

Examples

Basic usage:

let s = " Hello\tworld\t";

assert_eq!(" Hello\tworld", s.trim_right());
Run

Directionality:

let s = "English  ";
assert!(Some('h') == s.trim_right().chars().rev().next());

let s = "עברית  ";
assert!(Some('ת') == s.trim_right().chars().rev().next());
Run
source

pub fn trim_matches<'a, P>(&'a self, pat: P) -> &'a strwhere
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: DoubleEndedSearcher<'a>,

Returns a string slice with all prefixes and suffixes that match a pattern repeatedly removed.

The pattern can be a char, a slice of chars, or a function or closure that determines if a character matches.

Examples

Simple patterns:

assert_eq!("11foo1bar11".trim_matches('1'), "foo1bar");
assert_eq!("123foo1bar123".trim_matches(char::is_numeric), "foo1bar");

let x: &[_] = &['1', '2'];
assert_eq!("12foo1bar12".trim_matches(x), "foo1bar");
Run

A more complex pattern, using a closure:

assert_eq!("1foo1barXX".trim_matches(|c| c == '1' || c == 'X'), "foo1bar");
Run
1.30.0 · source

pub fn trim_start_matches<'a, P>(&'a self, pat: P) -> &'a strwhere
    P: Pattern<'a>,

Returns a string slice with all prefixes that match a pattern repeatedly removed.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Text directionality

A string is a sequence of bytes. start in this context means the first position of that byte string; for a left-to-right language like English or Russian, this will be left side, and for right-to-left languages like Arabic or Hebrew, this will be the right side.

Examples

Basic usage:

assert_eq!("11foo1bar11".trim_start_matches('1'), "foo1bar11");
assert_eq!("123foo1bar123".trim_start_matches(char::is_numeric), "foo1bar123");

let x: &[_] = &['1', '2'];
assert_eq!("12foo1bar12".trim_start_matches(x), "foo1bar12");
Run
1.45.0 · source

pub fn strip_prefix<'a, P>(&'a self, prefix: P) -> Option<&'a str>where
    P: Pattern<'a>,

Returns a string slice with the prefix removed.

If the string starts with the pattern prefix, returns substring after the prefix, wrapped in Some. Unlike trim_start_matches, this method removes the prefix exactly once.

If the string does not start with prefix, returns None.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Examples
assert_eq!("foo:bar".strip_prefix("foo:"), Some("bar"));
assert_eq!("foo:bar".strip_prefix("bar"), None);
assert_eq!("foofoo".strip_prefix("foo"), Some("foo"));
Run
1.45.0 · source

pub fn strip_suffix<'a, P>(&'a self, suffix: P) -> Option<&'a str>where
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,

Returns a string slice with the suffix removed.

If the string ends with the pattern suffix, returns the substring before the suffix, wrapped in Some. Unlike trim_end_matches, this method removes the suffix exactly once.

If the string does not end with suffix, returns None.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Examples
assert_eq!("bar:foo".strip_suffix(":foo"), Some("bar"));
assert_eq!("bar:foo".strip_suffix("bar"), None);
assert_eq!("foofoo".strip_suffix("foo"), Some("foo"));
Run
1.30.0 · source

pub fn trim_end_matches<'a, P>(&'a self, pat: P) -> &'a strwhere
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,

Returns a string slice with all suffixes that match a pattern repeatedly removed.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Text directionality

A string is a sequence of bytes. end in this context means the last position of that byte string; for a left-to-right language like English or Russian, this will be right side, and for right-to-left languages like Arabic or Hebrew, this will be the left side.

Examples

Simple patterns:

assert_eq!("11foo1bar11".trim_end_matches('1'), "11foo1bar");
assert_eq!("123foo1bar123".trim_end_matches(char::is_numeric), "123foo1bar");

let x: &[_] = &['1', '2'];
assert_eq!("12foo1bar12".trim_end_matches(x), "12foo1bar");
Run

A more complex pattern, using a closure:

assert_eq!("1fooX".trim_end_matches(|c| c == '1' || c == 'X'), "1foo");
Run
source

pub fn trim_left_matches<'a, P>(&'a self, pat: P) -> &'a strwhere
    P: Pattern<'a>,

👎Deprecated since 1.33.0: superseded by trim_start_matches

Returns a string slice with all prefixes that match a pattern repeatedly removed.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Text directionality

A string is a sequence of bytes. ‘Left’ in this context means the first position of that byte string; for a language like Arabic or Hebrew which are ‘right to left’ rather than ‘left to right’, this will be the right side, not the left.

Examples

Basic usage:

assert_eq!("11foo1bar11".trim_left_matches('1'), "foo1bar11");
assert_eq!("123foo1bar123".trim_left_matches(char::is_numeric), "foo1bar123");

let x: &[_] = &['1', '2'];
assert_eq!("12foo1bar12".trim_left_matches(x), "foo1bar12");
Run
source

pub fn trim_right_matches<'a, P>(&'a self, pat: P) -> &'a strwhere
    P: Pattern<'a>,
    <P as Pattern<'a>>::Searcher: ReverseSearcher<'a>,

👎Deprecated since 1.33.0: superseded by trim_end_matches

Returns a string slice with all suffixes that match a pattern repeatedly removed.

The pattern can be a &str, char, a slice of chars, or a function or closure that determines if a character matches.

Text directionality

A string is a sequence of bytes. ‘Right’ in this context means the last position of that byte string; for a language like Arabic or Hebrew which are ‘right to left’ rather than ‘left to right’, this will be the left side, not the right.

Examples

Simple patterns:

assert_eq!("11foo1bar11".trim_right_matches('1'), "11foo1bar");
assert_eq!("123foo1bar123".trim_right_matches(char::is_numeric), "123foo1bar");

let x: &[_] = &['1', '2'];
assert_eq!("12foo1bar12".trim_right_matches(x), "12foo1bar");
Run

A more complex pattern, using a closure:

assert_eq!("1fooX".trim_right_matches(|c| c == '1' || c == 'X'), "1foo");
Run
source

pub fn parse<F>(&self) -> Result<F, <F as FromStr>::Err>where
    F: FromStr,

Parses this string slice into another type.

Because parse is so general, it can cause problems with type inference. As such, parse is one of the few times you’ll see the syntax affectionately known as the ‘turbofish’: ::<>. This helps the inference algorithm understand specifically which type you’re trying to parse into.

parse can parse into any type that implements the FromStr trait.

Errors

Will return Err if it’s not possible to parse this string slice into the desired type.

Examples

Basic usage

let four: u32 = "4".parse().unwrap();

assert_eq!(4, four);
Run

Using the ‘turbofish’ instead of annotating four:

let four = "4".parse::<u32>();

assert_eq!(Ok(4), four);
Run

Failing to parse:

let nope = "j".parse::<u32>();

assert!(nope.is_err());
Run
1.23.0 · source

pub fn is_ascii(&self) -> bool

Checks if all characters in this string are within the ASCII range.

Examples
let ascii = "hello!\n";
let non_ascii = "Grüße, Jürgen ❤";

assert!(ascii.is_ascii());
assert!(!non_ascii.is_ascii());
Run
1.23.0 · source

pub fn eq_ignore_ascii_case(&self, other: &str) -> bool

Checks that two strings are an ASCII case-insensitive match.

Same as to_ascii_lowercase(a) == to_ascii_lowercase(b), but without allocating and copying temporaries.

Examples
assert!("Ferris".eq_ignore_ascii_case("FERRIS"));
assert!("Ferrös".eq_ignore_ascii_case("FERRöS"));
assert!(!"Ferrös".eq_ignore_ascii_case("FERRÖS"));
Run
1.23.0 · source

pub fn make_ascii_uppercase(&mut self)

Converts this string to its ASCII upper case equivalent in-place.

ASCII letters ‘a’ to ‘z’ are mapped to ‘A’ to ‘Z’, but non-ASCII letters are unchanged.

To return a new uppercased value without modifying the existing one, use to_ascii_uppercase().

Examples
let mut s = String::from("Grüße, Jürgen ❤");

s.make_ascii_uppercase();

assert_eq!("GRüßE, JüRGEN ❤", s);
Run
1.23.0 · source

pub fn make_ascii_lowercase(&mut self)

Converts this string to its ASCII lower case equivalent in-place.

ASCII letters ‘A’ to ‘Z’ are mapped to ‘a’ to ‘z’, but non-ASCII letters are unchanged.

To return a new lowercased value without modifying the existing one, use to_ascii_lowercase().

Examples
let mut s = String::from("GRÜßE, JÜRGEN ❤");

s.make_ascii_lowercase();

assert_eq!("grÜße, jÜrgen ❤", s);
Run
1.34.0 · source

pub fn escape_debug(&self) -> EscapeDebug<'_>

Return an iterator that escapes each char in self with char::escape_debug.

Note: only extended grapheme codepoints that begin the string will be escaped.

Examples

As an iterator:

for c in "❤\n!".escape_debug() {
    print!("{c}");
}
println!();
Run

Using println! directly:

println!("{}", "❤\n!".escape_debug());
Run

Both are equivalent to:

println!("❤\\n!");
Run

Using to_string:

assert_eq!("❤\n!".escape_debug().to_string(), "❤\\n!");
Run
1.34.0 · source

pub fn escape_default(&self) -> EscapeDefault<'_>

Return an iterator that escapes each char in self with char::escape_default.

Examples

As an iterator:

for c in "❤\n!".escape_default() {
    print!("{c}");
}
println!();
Run

Using println! directly:

println!("{}", "❤\n!".escape_default());
Run

Both are equivalent to:

println!("\\u{{2764}}\\n!");
Run

Using to_string:

assert_eq!("❤\n!".escape_default().to_string(), "\\u{2764}\\n!");
Run
1.34.0 · source

pub fn escape_unicode(&self) -> EscapeUnicode<'_>

Return an iterator that escapes each char in self with char::escape_unicode.

Examples

As an iterator:

for c in "❤\n!".escape_unicode() {
    print!("{c}");
}
println!();
Run

Using println! directly:

println!("{}", "❤\n!".escape_unicode());
Run

Both are equivalent to:

println!("\\u{{2764}}\\u{{a}}\\u{{21}}");
Run

Using to_string:

assert_eq!("❤\n!".escape_unicode().to_string(), "\\u{2764}\\u{a}\\u{21}");
Run
source§

impl str

Methods for string slices.

1.20.0 · source

pub fn into_boxed_bytes(self: Box<str, Global>) -> Box<[u8], Global>

Converts a Box<str> into a Box<[u8]> without copying or allocating.

Examples

Basic usage:

let s = "this is a string";
let boxed_str = s.to_owned().into_boxed_str();
let boxed_bytes = boxed_str.into_boxed_bytes();
assert_eq!(*boxed_bytes, *s.as_bytes());
Run
source

pub fn replace<'a, P>(&'a self, from: P, to: &str) -> Stringwhere
    P: Pattern<'a>,

Replaces all matches of a pattern with another string.

replace creates a new String, and copies the data from this string slice into it. While doing so, it attempts to find matches of a pattern. If it finds any, it replaces them with the replacement string slice.

Examples

Basic usage:

let s = "this is old";

assert_eq!("this is new", s.replace("old", "new"));
assert_eq!("than an old", s.replace("is", "an"));
Run

When the pattern doesn’t match:

let s = "this is old";
assert_eq!(s, s.replace("cookie monster", "little lamb"));
Run
1.16.0 · source

pub fn replacen<'a, P>(&'a self, pat: P, to: &str, count: usize) -> Stringwhere
    P: Pattern<'a>,

Replaces first N matches of a pattern with another string.

replacen creates a new String, and copies the data from this string slice into it. While doing so, it attempts to find matches of a pattern. If it finds any, it replaces them with the replacement string slice at most count times.

Examples

Basic usage:

let s = "foo foo 123 foo";
assert_eq!("new new 123 foo", s.replacen("foo", "new", 2));
assert_eq!("faa fao 123 foo", s.replacen('o', "a", 3));
assert_eq!("foo foo new23 foo", s.replacen(char::is_numeric, "new", 1));
Run

When the pattern doesn’t match:

let s = "this is old";
assert_eq!(s, s.replacen("cookie monster", "little lamb", 10));
Run
1.2.0 · source

pub fn to_lowercase(&self) -> String

Returns the lowercase equivalent of this string slice, as a new String.

‘Lowercase’ is defined according to the terms of the Unicode Derived Core Property Lowercase.

Since some characters can expand into multiple characters when changing the case, this function returns a String instead of modifying the parameter in-place.

Examples

Basic usage:

let s = "HELLO";

assert_eq!("hello", s.to_lowercase());
Run

A tricky example, with sigma:

let sigma = "Σ";

assert_eq!("σ", sigma.to_lowercase());

// but at the end of a word, it's ς, not σ:
let odysseus = "ὈΔΥΣΣΕΎΣ";

assert_eq!("ὀδυσσεύς", odysseus.to_lowercase());
Run

Languages without case are not changed:

let new_year = "农历新年";

assert_eq!(new_year, new_year.to_lowercase());
Run
1.2.0 · source

pub fn to_uppercase(&self) -> String

Returns the uppercase equivalent of this string slice, as a new String.

‘Uppercase’ is defined according to the terms of the Unicode Derived Core Property Uppercase.

Since some characters can expand into multiple characters when changing the case, this function returns a String instead of modifying the parameter in-place.

Examples

Basic usage:

let s = "hello";

assert_eq!("HELLO", s.to_uppercase());
Run

Scripts without case are not changed:

let new_year = "农历新年";

assert_eq!(new_year, new_year.to_uppercase());
Run

One character can become multiple:

let s = "tschüß";

assert_eq!("TSCHÜSS", s.to_uppercase());
Run
1.4.0 · source

pub fn into_string(self: Box<str, Global>) -> String

Converts a Box<str> into a String without copying or allocating.

Examples

Basic usage:

let string = String::from("birthday gift");
let boxed_str = string.clone().into_boxed_str();

assert_eq!(boxed_str.into_string(), string);
Run
1.16.0 · source

pub fn repeat(&self, n: usize) -> String

Creates a new String by repeating a string n times.

Panics

This function will panic if the capacity would overflow.

Examples

Basic usage:

assert_eq!("abc".repeat(4), String::from("abcabcabcabc"));
Run

A panic upon overflow:

// this will panic at runtime
let huge = "0123456789abcdef".repeat(usize::MAX);
Run
1.23.0 · source

pub fn to_ascii_uppercase(&self) -> String

Returns a copy of this string where each character is mapped to its ASCII upper case equivalent.

ASCII letters ‘a’ to ‘z’ are mapped to ‘A’ to ‘Z’, but non-ASCII letters are unchanged.

To uppercase the value in-place, use make_ascii_uppercase.

To uppercase ASCII characters in addition to non-ASCII characters, use to_uppercase.

Examples
let s = "Grüße, Jürgen ❤";

assert_eq!("GRüßE, JüRGEN ❤", s.to_ascii_uppercase());
Run
1.23.0 · source

pub fn to_ascii_lowercase(&self) -> String

Returns a copy of this string where each character is mapped to its ASCII lower case equivalent.

ASCII letters ‘A’ to ‘Z’ are mapped to ‘a’ to ‘z’, but non-ASCII letters are unchanged.

To lowercase the value in-place, use make_ascii_lowercase.

To lowercase ASCII characters in addition to non-ASCII characters, use to_lowercase.

Examples
let s = "Grüße, Jürgen ❤";

assert_eq!("grüße, jürgen ❤", s.to_ascii_lowercase());
Run

Trait Implementations§

1.14.0 · source§

impl<'a> Add<&'a str> for Cow<'a, str>

§

type Output = Cow<'a, str>

The resulting type after applying the + operator.
source§

fn add(self, rhs: &'a str) -> <Cow<'a, str> as Add<&'a str>>::Output

Performs the + operation. Read more
source§

impl Add<&str> for String

Implements the + operator for concatenating two strings.

This consumes the String on the left-hand side and re-uses its buffer (growing it if necessary). This is done to avoid allocating a new String and copying the entire contents on every operation, which would lead to O(n^2) running time when building an n-byte string by repeated concatenation.

The string on the right-hand side is only borrowed; its contents are copied into the returned String.

Examples

Concatenating two Strings takes the first by value and borrows the second:

let a = String::from("hello");
let b = String::from(" world");
let c = a + &b;
// `a` is moved and can no longer be used here.
Run

If you want to keep using the first String, you can clone it and append to the clone instead:

let a = String::from("hello");
let b = String::from(" world");
let c = a.clone() + &b;
// `a` is still valid here.
Run

Concatenating &str slices can be done by converting the first to a String:

let a = "hello";
let b = " world";
let c = a.to_string() + b;
Run
§

type Output = String

The resulting type after applying the + operator.
source§

fn add(self, other: &str) -> String

Performs the + operation. Read more
1.14.0 · source§

impl<'a> AddAssign<&'a str> for Cow<'a, str>

source§

fn add_assign(&mut self, rhs: &'a str)

Performs the += operation. Read more
1.12.0 · source§

impl AddAssign<&str> for String

Implements the += operator for appending to a String.

This has the same behavior as the push_str method.

source§

fn add_assign(&mut self, other: &str)

Performs the += operation. Read more
1.43.0 · source§

impl AsMut<str> for String

source§

fn as_mut(&mut self) -> &mut str

Converts this type into a mutable reference of the (usually inferred) input type.
1.51.0 · source§

impl AsMut<str> for str

source§

fn as_mut(&mut self) -> &mut str

Converts this type into a mutable reference of the (usually inferred) input type.
source§

impl AsRef<[u8]> for str

source§

fn as_ref(&self) -> &[u8]

Converts this type into a shared reference of the (usually inferred) input type.
source§

impl AsRef<OsStr> for str

source§

fn as_ref(&self) -> &OsStr

Converts this type into a shared reference of the (usually inferred) input type.
source§

impl AsRef<Path> for str

source§

fn as_ref(&self) -> &Path

Converts this type into a shared reference of the (usually inferred) input type.
1.55.0 · source§

impl<'a> AsRef<str> for Drain<'a>

source§

fn as_ref(&self) -> &str

Converts this type into a shared reference of the (usually inferred) input type.
source§

impl AsRef<str> for String

source§

fn as_ref(&self) -> &str

Converts this type into a shared reference of the (usually inferred) input type.
source§

impl AsRef<str> for str

source§

fn as_ref(&self) -> &str

Converts this type into a shared reference of the (usually inferred) input type.
source§

impl AsciiExt for str

§

type Owned = String

👎Deprecated since 1.26.0: use inherent methods instead
Container type for copied ASCII characters.
source§

fn is_ascii(&self) -> bool

👎Deprecated since 1.26.0: use inherent methods instead
Checks if the value is within the ASCII range. Read more
source§

fn to_ascii_uppercase(&self) -> Self::Owned

👎Deprecated since 1.26.0: use inherent methods instead
Makes a copy of the value in its ASCII upper case equivalent. Read more
source§

fn to_ascii_lowercase(&self) -> Self::Owned

👎Deprecated since 1.26.0: use inherent methods instead
Makes a copy of the value in its ASCII lower case equivalent. Read more
source§

fn eq_ignore_ascii_case(&self, o: &Self) -> bool

👎Deprecated since 1.26.0: use inherent methods instead
Checks that two values are an ASCII case-insensitive match. Read more
source§

fn make_ascii_uppercase(&mut self)

👎Deprecated since 1.26.0: use inherent methods instead
Converts this type to its ASCII upper case equivalent in-place. Read more
source§

fn make_ascii_lowercase(&mut self)

👎Deprecated since 1.26.0: use inherent methods instead
Converts this type to its ASCII lower case equivalent in-place. Read more
source§

impl Borrow<str> for String

source§

fn borrow(&self) -> &str

Immutably borrows from an owned value. Read more
1.36.0 · source§

impl BorrowMut<str> for String

source§

fn borrow_mut(&mut self) -> &mut str

Mutably borrows from an owned value. Read more
1.3.0 · source§

impl Clone for Box<str, Global>

source§

fn clone(&self) -> Box<str, Global>

Returns a copy of the value. Read more
source§

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
source§

impl<S> Concat<str> for [S]where
    S: Borrow<str>,

Note: str in Concat<str> is not meaningful here. This type parameter of the trait only exists to enable another impl.

§

type Output = String

🔬This is a nightly-only experimental API. (slice_concat_trait #27747)
The resulting type after concatenation
source§

fn concat(slice: &[S]) -> String

🔬This is a nightly-only experimental API. (slice_concat_trait #27747)
Implementation of [T]::concat
source§

impl Debug for str

source§

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more
1.28.0 · source§

impl Default for &mut str

source§

fn default() -> &mut str

Creates an empty mutable str

const: unstable · source§

impl Default for &str

const: unstable · source§

fn default() -> &str

Creates an empty str

1.17.0 (const: unstable) · source§

impl Default for Box<str, Global>

const: unstable · source§

fn default() -> Box<str, Global>

Returns the “default value” for a type. Read more
source§

impl Display for str

source§

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more
source§

impl !Error for &str

1.30.0 · source§

fn source(&self) -> Option<&(dyn Error + 'static)>

The lower-level source of this error, if any. Read more
source§

fn description(&self) -> &str

👎Deprecated since 1.42.0: use the Display impl or to_string()
source§

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0: replaced by Error::source, which can support downcasting
source§

fn provide<'a>(&'a self, demand: &mut Demand<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access #99301)
Provides type based access to context intended for error reports. Read more
source§

impl<'a> Extend<&'a str> for String

source§

fn extend<I>(&mut self, iter: I)where
    I: IntoIterator<Item = &'a str>,

Extends a collection with the contents of an iterator. Read more
source§

fn extend_one(&mut self, s: &'a str)

🔬This is a nightly-only experimental API. (extend_one #72631)
Extends a collection with exactly one element.
source§

fn extend_reserve(&mut self, additional: usize)

🔬This is a nightly-only experimental API. (extend_one #72631)
Reserves capacity in a collection for the given number of additional elements. Read more
source§

impl<'a> From<&'a str> for Cow<'a, str>

source§

fn from(s: &'a str) -> Cow<'a, str>

Converts a string slice into a Borrowed variant. No heap allocation is performed, and the string is not copied.

Example
assert_eq!(Cow::from("eggplant"), Cow::Borrowed("eggplant"));
Run
1.44.0 · source§

impl From<&mut str> for String

source§

fn from(s: &mut str) -> String

Converts a &mut str into a String.

The result is allocated on the heap.

1.21.0 · source§

impl From<&str> for Arc<str>

source§

fn from(v: &str) -> Arc<str>

Allocate a reference-counted str and copy v into it.

Example
let shared: Arc<str> = Arc::from("eggplant");
assert_eq!("eggplant", &shared[..]);
Run
1.6.0 · source§

impl From<&str> for Box<dyn Error + 'static, Global>

source§

fn from(err: &str) -> Box<dyn Error + 'static, Global>

Converts a str into a box of dyn Error.

Examples
use std::error::Error;
use std::mem;

let a_str_error = "a str error";
let a_boxed_error = Box::<dyn Error>::from(a_str_error);
assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))
Run
source§

impl<'a> From<&str> for Box<dyn Error + Send + Sync + 'a, Global>

source§

fn from(err: &str) -> Box<dyn Error + Send + Sync + 'a, Global>

Converts a str into a box of dyn Error + Send + Sync.

Examples
use std::error::Error;
use std::mem;

let a_str_error = "a str error";
let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_str_error);
assert!(
    mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
Run
1.17.0 · source§

impl From<&str> for Box<str, Global>

source§

fn from(s: &str) -> Box<str, Global>

Converts a &str into a Box<str>

This conversion allocates on the heap and performs a copy of s.

Examples
let boxed: Box<str> = Box::from("hello");
println!("{boxed}");
Run
1.21.0 · source§

impl From<&str> for Rc<str>

source§

fn from(v: &str) -> Rc<str>

Allocate a reference-counted string slice and copy v into it.

Example
let shared: Rc<str> = Rc::from("statue");
assert_eq!("statue", &shared[..]);
Run
source§

impl From<&str> for String

source§

fn from(s: &str) -> String

Converts a &str into a String.

The result is allocated on the heap.

source§

impl From<&str> for Vec<u8, Global>

source§

fn from(s: &str) -> Vec<u8, Global>

Allocate a Vec<u8> and fill it with a UTF-8 string.

Examples
assert_eq!(Vec::from("123"), vec![b'1', b'2', b'3']);
Run
1.45.0 · source§

impl From<Cow<'_, str>> for Box<str, Global>

source§

fn from(cow: Cow<'_, str>) -> Box<str, Global>

Converts a Cow<'_, str> into a Box<str>

When cow is the Cow::Borrowed variant, this conversion allocates on the heap and copies the underlying str. Otherwise, it will try to reuse the owned String’s allocation.

Examples
use std::borrow::Cow;

let unboxed = Cow::Borrowed("hello");
let boxed: Box<str> = Box::from(unboxed);
println!("{boxed}");
Run
let unboxed = Cow::Owned("hello".to_string());
let boxed: Box<str> = Box::from(unboxed);
println!("{boxed}");
Run
1.20.0 · source§

impl From<String> for Box<str, Global>

source§

fn from(s: String) -> Box<str, Global>

Converts the given String to a boxed str slice that is owned.

Examples

Basic usage:

let s1: String = String::from("hello world");
let s2: Box<str> = Box::from(s1);
let s3: String = String::from(s2);

assert_eq!("hello world", s3)
Run
source§

impl<'a> FromIterator<&'a str> for String

source§

fn from_iter<I>(iter: I) -> Stringwhere
    I: IntoIterator<Item = &'a str>,

Creates a value from an iterator. Read more
1.12.0 · source§

impl<'a, 'b> FromIterator<&'b str> for Cow<'a, str>

source§

fn from_iter<I>(it: I) -> Cow<'a, str>where
    I: IntoIterator<Item = &'b str>,

Creates a value from an iterator. Read more
const: unstable · source§

impl Hash for str

const: unstable · source§

fn hash<H>(&self, state: &mut H)where
    H: Hasher,

Feeds this value into the given Hasher. Read more
const: unstable · source§

impl<I> Index<I> for strwhere
    I: SliceIndex<str>,

§

type Output = <I as SliceIndex<str>>::Output

The returned type after indexing.
const: unstable · source§

fn index(&self, index: I) -> &<I as SliceIndex<str>>::Output

Performs the indexing (container[index]) operation. Read more
const: unstable · source§

impl<I> IndexMut<I> for strwhere
    I: SliceIndex<str>,

const: unstable · source§

fn index_mut(&mut self, index: I) -> &mut <I as SliceIndex<str>>::Output

Performs the mutable indexing (container[index]) operation. Read more
source§

impl<S> Join<&str> for [S]where
    S: Borrow<str>,

§

type Output = String

🔬This is a nightly-only experimental API. (slice_concat_trait #27747)
The resulting type after concatenation
source§

fn join(slice: &[S], sep: &str) -> String

🔬This is a nightly-only experimental API. (slice_concat_trait #27747)
Implementation of [T]::join
source§

impl Ord for str

Implements ordering of strings.

Strings are ordered lexicographically by their byte values. This orders Unicode code points based on their positions in the code charts. This is not necessarily the same as “alphabetical” order, which varies by language and locale. Sorting strings according to culturally-accepted standards requires locale-specific data that is outside the scope of the str type.

source§

fn cmp(&self, other: &str) -> Ordering

This method returns an Ordering between self and other. Read more
source§

impl<'a, 'b> PartialEq<&'a str> for String

source§

fn eq(&self, other: &&'a str) -> bool

This method tests for self and other values to be equal, and is used by ==.
source§

fn ne(&self, other: &&'a str) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source§

impl<'a, 'b> PartialEq<&'b str> for Cow<'a, str>

source§

fn eq(&self, other: &&'b str) -> bool

This method tests for self and other values to be equal, and is used by ==.
source§

fn ne(&self, other: &&'b str) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
1.29.0 · source§

impl PartialEq<&str> for OsString

source§

fn eq(&self, other: &&str) -> bool

This method tests for self and other values to be equal, and is used by ==.
source§

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source§

impl<'a, 'b> PartialEq<Cow<'a, str>> for &'b str

source§

fn eq(&self, other: &Cow<'a, str>) -> bool

This method tests for self and other values to be equal, and is used by ==.
source§

fn ne(&self, other: &Cow<'a, str>) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source§

impl<'a, 'b> PartialEq<Cow<'a, str>> for str

source§

fn eq(&self, other: &Cow<'a, str>) -> bool

This method tests for self and other values to be equal, and is used by ==.
source§

fn ne(&self, other: &Cow<'a, str>) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source§

impl PartialEq<OsStr> for str

source§

fn eq(&self, other: &OsStr) -> bool

This method tests for self and other values to be equal, and is used by ==.
source§

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
1.29.0 · source§

impl<'a> PartialEq<OsString> for &'a str

source§

fn eq(&self, other: &OsString) -> bool

This method tests for self and other values to be equal, and is used by ==.
source§

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source§

impl PartialEq<OsString> for str

source§

fn eq(&self, other: &OsString) -> bool

This method tests for self and other values to be equal, and is used by ==.
source§

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source§

impl<'a, 'b> PartialEq<String> for &'a str

source§

fn eq(&self, other: &String) -> bool

This method tests for self and other values to be equal, and is used by ==.
source§

fn ne(&self, other: &String) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source§

impl<'a, 'b> PartialEq<String> for str

source§

fn eq(&self, other: &String) -> bool

This method tests for self and other values to be equal, and is used by ==.
source§

fn ne(&self, other: &String) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source§

impl<'a, 'b> PartialEq<str> for Cow<'a, str>

source§

fn eq(&self, other: &str) -> bool

This method tests for self and other values to be equal, and is used by ==.
source§

fn ne(&self, other: &str) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source§

impl PartialEq<str> for OsStr

source§

fn eq(&self, other: &str) -> bool

This method tests for self and other values to be equal, and is used by ==.
source§

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source§

impl PartialEq<str> for OsString

source§

fn eq(&self, other: &str) -> bool

This method tests for self and other values to be equal, and is used by ==.
source§

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source§

impl<'a, 'b> PartialEq<str> for String

source§

fn eq(&self, other: &str) -> bool

This method tests for self and other values to be equal, and is used by ==.
source§

fn ne(&self, other: &str) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source§

impl PartialEq<str> for str

source§

fn eq(&self, other: &str) -> bool

This method tests for self and other values to be equal, and is used by ==.
source§

fn ne(&self, other: &str) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source§

impl PartialOrd<str> for OsStr

source§

fn partial_cmp(&self, other: &str) -> Option<Ordering>

This method returns an ordering between self and other values if one exists. Read more
source§

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator. Read more
source§

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more
source§

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator. Read more
source§

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more
source§

impl PartialOrd<str> for OsString

source§

fn partial_cmp(&self, other: &str) -> Option<Ordering>

This method returns an ordering between self and other values if one exists. Read more
source§

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator. Read more
source§

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more
source§

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator. Read more
source§

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more
source§

impl PartialOrd<str> for str

Implements comparison operations on strings.

Strings are compared lexicographically by their byte values. This compares Unicode code points based on their positions in the code charts. This is not necessarily the same as “alphabetical” order, which varies by language and locale. Comparing strings according to culturally-accepted standards requires locale-specific data that is outside the scope of the str type.

source§

fn partial_cmp(&self, other: &str) -> Option<Ordering>

This method returns an ordering between self and other values if one exists. Read more
source§

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator. Read more
source§

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more
source§

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator. Read more
source§

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more
source§

impl<'a, 'b> Pattern<'a> for &'b str

Non-allocating substring search.

Will handle the pattern "" as returning empty matches at each character boundary.

Examples

assert_eq!("Hello world".find("world"), Some(6));
Run
source§

fn is_prefix_of(self, haystack: &'a str) -> bool

🔬This is a nightly-only experimental API. (pattern #27721)

Checks whether the pattern matches at the front of the haystack.

source§

fn is_contained_in(self, haystack: &'a str) -> bool

🔬This is a nightly-only experimental API. (pattern #27721)

Checks whether the pattern matches anywhere in the haystack

source§

fn strip_prefix_of(self, haystack: &'a str) -> Option<&'a str>

🔬This is a nightly-only experimental API. (pattern #27721)

Removes the pattern from the front of haystack, if it matches.

source§

fn is_suffix_of(self, haystack: &'a str) -> bool

🔬This is a nightly-only experimental API. (pattern #27721)

Checks whether the pattern matches at the back of the haystack.

source§

fn strip_suffix_of(self, haystack: &'a str) -> Option<&'a str>

🔬This is a nightly-only experimental API. (pattern #27721)

Removes the pattern from the back of haystack, if it matches.

§

type Searcher = StrSearcher<'a, 'b>

🔬This is a nightly-only experimental API. (pattern #27721)
Associated searcher for this pattern
source§

fn into_searcher(self, haystack: &'a str) -> StrSearcher<'a, 'b>

🔬This is a nightly-only experimental API. (pattern #27721)
Constructs the associated searcher from self and the haystack to search in.
1.20.0 (const: unstable) · source§

impl SliceIndex<str> for Range<usize>

Implements substring slicing with syntax &self[begin .. end] or &mut self[begin .. end].

Returns a slice of the given string from the byte range [begin, end).

This operation is O(1).

Prior to 1.20.0, these indexing operations were still supported by direct implementation of Index and IndexMut.

Panics

Panics if begin or end does not point to the starting byte offset of a character (as defined by is_char_boundary), if begin > end, or if end > len.

Examples

let s = "Löwe 老虎 Léopard";
assert_eq!(&s[0 .. 1], "L");

assert_eq!(&s[1 .. 9], "öwe 老");

// these will panic:
// byte 2 lies within `ö`:
// &s[2 ..3];

// byte 8 lies within `老`
// &s[1 .. 8];

// byte 100 is outside the string
// &s[3 .. 100];
Run
§

type Output = str

The output type returned by methods.
const: unstable · source§

fn get(self, slice: &str) -> Option<&<Range<usize> as SliceIndex<str>>::Output>

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a shared reference to the output at this location, if in bounds.
const: unstable · source§

fn get_mut(
    self,
    slice: &mut str
) -> Option<&mut <Range<usize> as SliceIndex<str>>::Output>

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a mutable reference to the output at this location, if in bounds.
const: unstable · source§

unsafe fn get_unchecked(
    self,
    slice: *const str
) -> *const <Range<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a shared reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index or a dangling slice pointer is undefined behavior even if the resulting reference is not used.
const: unstable · source§

unsafe fn get_unchecked_mut(
    self,
    slice: *mut str
) -> *mut <Range<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a mutable reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index or a dangling slice pointer is undefined behavior even if the resulting reference is not used.
const: unstable · source§

fn index(self, slice: &str) -> &<Range<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a shared reference to the output at this location, panicking if out of bounds.
const: unstable · source§

fn index_mut(
    self,
    slice: &mut str
) -> &mut <Range<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a mutable reference to the output at this location, panicking if out of bounds.
1.20.0 (const: unstable) · source§

impl SliceIndex<str> for RangeFrom<usize>

Implements substring slicing with syntax &self[begin ..] or &mut self[begin ..].

Returns a slice of the given string from the byte range [begin, len). Equivalent to &self[begin .. len] or &mut self[begin .. len].

This operation is O(1).

Prior to 1.20.0, these indexing operations were still supported by direct implementation of Index and IndexMut.

Panics

Panics if begin does not point to the starting byte offset of a character (as defined by is_char_boundary), or if begin > len.

§

type Output = str

The output type returned by methods.
const: unstable · source§

fn get(
    self,
    slice: &str
) -> Option<&<RangeFrom<usize> as SliceIndex<str>>::Output>

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a shared reference to the output at this location, if in bounds.
const: unstable · source§

fn get_mut(
    self,
    slice: &mut str
) -> Option<&mut <RangeFrom<usize> as SliceIndex<str>>::Output>

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a mutable reference to the output at this location, if in bounds.
const: unstable · source§

unsafe fn get_unchecked(
    self,
    slice: *const str
) -> *const <RangeFrom<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a shared reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index or a dangling slice pointer is undefined behavior even if the resulting reference is not used.
const: unstable · source§

unsafe fn get_unchecked_mut(
    self,
    slice: *mut str
) -> *mut <RangeFrom<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a mutable reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index or a dangling slice pointer is undefined behavior even if the resulting reference is not used.
const: unstable · source§

fn index(self, slice: &str) -> &<RangeFrom<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a shared reference to the output at this location, panicking if out of bounds.
const: unstable · source§

fn index_mut(
    self,
    slice: &mut str
) -> &mut <RangeFrom<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a mutable reference to the output at this location, panicking if out of bounds.
1.20.0 (const: unstable) · source§

impl SliceIndex<str> for RangeFull

Implements substring slicing with syntax &self[..] or &mut self[..].

Returns a slice of the whole string, i.e., returns &self or &mut self. Equivalent to &self[0 .. len] or &mut self[0 .. len]. Unlike other indexing operations, this can never panic.

This operation is O(1).

Prior to 1.20.0, these indexing operations were still supported by direct implementation of Index and IndexMut.

Equivalent to &self[0 .. len] or &mut self[0 .. len].

§

type Output = str

The output type returned by methods.
const: unstable · source§

fn get(self, slice: &str) -> Option<&<RangeFull as SliceIndex<str>>::Output>

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a shared reference to the output at this location, if in bounds.
const: unstable · source§

fn get_mut(
    self,
    slice: &mut str
) -> Option<&mut <RangeFull as SliceIndex<str>>::Output>

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a mutable reference to the output at this location, if in bounds.
const: unstable · source§

unsafe fn get_unchecked(
    self,
    slice: *const str
) -> *const <RangeFull as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a shared reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index or a dangling slice pointer is undefined behavior even if the resulting reference is not used.
const: unstable · source§

unsafe fn get_unchecked_mut(
    self,
    slice: *mut str
) -> *mut <RangeFull as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a mutable reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index or a dangling slice pointer is undefined behavior even if the resulting reference is not used.
const: unstable · source§

fn index(self, slice: &str) -> &<RangeFull as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a shared reference to the output at this location, panicking if out of bounds.
const: unstable · source§

fn index_mut(
    self,
    slice: &mut str
) -> &mut <RangeFull as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a mutable reference to the output at this location, panicking if out of bounds.
1.26.0 (const: unstable) · source§

impl SliceIndex<str> for RangeInclusive<usize>

Implements substring slicing with syntax &self[begin ..= end] or &mut self[begin ..= end].

Returns a slice of the given string from the byte range [begin, end]. Equivalent to &self [begin .. end + 1] or &mut self[begin .. end + 1], except if end has the maximum value for usize.

This operation is O(1).

Panics

Panics if begin does not point to the starting byte offset of a character (as defined by is_char_boundary), if end does not point to the ending byte offset of a character (end + 1 is either a starting byte offset or equal to len), if begin > end, or if end >= len.

§

type Output = str

The output type returned by methods.
const: unstable · source§

fn get(
    self,
    slice: &str
) -> Option<&<RangeInclusive<usize> as SliceIndex<str>>::Output>

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a shared reference to the output at this location, if in bounds.
const: unstable · source§

fn get_mut(
    self,
    slice: &mut str
) -> Option<&mut <RangeInclusive<usize> as SliceIndex<str>>::Output>

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a mutable reference to the output at this location, if in bounds.
const: unstable · source§

unsafe fn get_unchecked(
    self,
    slice: *const str
) -> *const <RangeInclusive<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a shared reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index or a dangling slice pointer is undefined behavior even if the resulting reference is not used.
const: unstable · source§

unsafe fn get_unchecked_mut(
    self,
    slice: *mut str
) -> *mut <RangeInclusive<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a mutable reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index or a dangling slice pointer is undefined behavior even if the resulting reference is not used.
const: unstable · source§

fn index(
    self,
    slice: &str
) -> &<RangeInclusive<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a shared reference to the output at this location, panicking if out of bounds.
const: unstable · source§

fn index_mut(
    self,
    slice: &mut str
) -> &mut <RangeInclusive<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a mutable reference to the output at this location, panicking if out of bounds.
1.20.0 (const: unstable) · source§

impl SliceIndex<str> for RangeTo<usize>

Implements substring slicing with syntax &self[.. end] or &mut self[.. end].

Returns a slice of the given string from the byte range [0, end). Equivalent to &self[0 .. end] or &mut self[0 .. end].

This operation is O(1).

Prior to 1.20.0, these indexing operations were still supported by direct implementation of Index and IndexMut.

Panics

Panics if end does not point to the starting byte offset of a character (as defined by is_char_boundary), or if end > len.

§

type Output = str

The output type returned by methods.
const: unstable · source§

fn get(self, slice: &str) -> Option<&<RangeTo<usize> as SliceIndex<str>>::Output>

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a shared reference to the output at this location, if in bounds.
const: unstable · source§

fn get_mut(
    self,
    slice: &mut str
) -> Option<&mut <RangeTo<usize> as SliceIndex<str>>::Output>

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a mutable reference to the output at this location, if in bounds.
const: unstable · source§

unsafe fn get_unchecked(
    self,
    slice: *const str
) -> *const <RangeTo<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a shared reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index or a dangling slice pointer is undefined behavior even if the resulting reference is not used.
const: unstable · source§

unsafe fn get_unchecked_mut(
    self,
    slice: *mut str
) -> *mut <RangeTo<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a mutable reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index or a dangling slice pointer is undefined behavior even if the resulting reference is not used.
const: unstable · source§

fn index(self, slice: &str) -> &<RangeTo<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a shared reference to the output at this location, panicking if out of bounds.
const: unstable · source§

fn index_mut(
    self,
    slice: &mut str
) -> &mut <RangeTo<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a mutable reference to the output at this location, panicking if out of bounds.
1.26.0 (const: unstable) · source§

impl SliceIndex<str> for RangeToInclusive<usize>

Implements substring slicing with syntax &self[..= end] or &mut self[..= end].

Returns a slice of the given string from the byte range [0, end]. Equivalent to &self [0 .. end + 1], except if end has the maximum value for usize.

This operation is O(1).

Panics

Panics if end does not point to the ending byte offset of a character (end + 1 is either a starting byte offset as defined by is_char_boundary, or equal to len), or if end >= len.

§

type Output = str

The output type returned by methods.
const: unstable · source§

fn get(
    self,
    slice: &str
) -> Option<&<RangeToInclusive<usize> as SliceIndex<str>>::Output>

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a shared reference to the output at this location, if in bounds.
const: unstable · source§

fn get_mut(
    self,
    slice: &mut str
) -> Option<&mut <RangeToInclusive<usize> as SliceIndex<str>>::Output>

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a mutable reference to the output at this location, if in bounds.
const: unstable · source§

unsafe fn get_unchecked(
    self,
    slice: *const str
) -> *const <RangeToInclusive<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a shared reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index or a dangling slice pointer is undefined behavior even if the resulting reference is not used.
const: unstable · source§

unsafe fn get_unchecked_mut(
    self,
    slice: *mut str
) -> *mut <RangeToInclusive<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a mutable reference to the output at this location, without performing any bounds checking. Calling this method with an out-of-bounds index or a dangling slice pointer is undefined behavior even if the resulting reference is not used.
const: unstable · source§

fn index(
    self,
    slice: &str
) -> &<RangeToInclusive<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a shared reference to the output at this location, panicking if out of bounds.
const: unstable · source§

fn index_mut(
    self,
    slice: &mut str
) -> &mut <RangeToInclusive<usize> as SliceIndex<str>>::Output

🔬This is a nightly-only experimental API. (slice_index_methods)
Returns a mutable reference to the output at this location, panicking if out of bounds.
source§

impl ToOwned for str

§

type Owned = String

The resulting type after obtaining ownership.
source§

fn to_owned(&self) -> String

Creates owned data from borrowed data, usually by cloning. Read more
source§

fn clone_into(&self, target: &mut String)

Uses borrowed data to replace owned data, usually by cloning. Read more
source§

impl ToSocketAddrs for str

§

type Iter = IntoIter<SocketAddr, Global>

Returned iterator over socket addresses which this type may correspond to.
source§

fn to_socket_addrs(&self) -> Result<IntoIter<SocketAddr>>

Converts this object to an iterator of resolved SocketAddrs. Read more
1.9.0 · source§

impl ToString for str

source§

fn to_string(&self) -> String

Converts the given value to a String. Read more
source§

impl Eq for str

Auto Trait Implementations§

§

impl RefUnwindSafe for str

§

impl Send for str

§

impl !Sized for str

§

impl Sync for str

§

impl Unpin for str

§

impl UnwindSafe for str

Blanket Implementations§

source§

impl<T> Any for Twhere
    T: 'static + ?Sized,

source§

fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
source§

impl<T> Borrow<T> for Twhere
    T: ?Sized,

const: unstable · source§

fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
source§

impl<T> BorrowMut<T> for Twhere
    T: ?Sized,

const: unstable · source§

fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
source§

impl<T> ToString for Twhere
    T: Display + ?Sized,

source§

default fn to_string(&self) -> String

Converts the given value to a String. Read more