Trait tracing::stdlib::iter::Extend

1.0.0 · source ·
pub trait Extend<A> {
    // Required method
    fn extend<T>(&mut self, iter: T)
       where T: IntoIterator<Item = A>;

    // Provided methods
    fn extend_one(&mut self, item: A) { ... }
    fn extend_reserve(&mut self, additional: usize) { ... }
}
Expand description

Extend a collection with the contents of an iterator.

Iterators produce a series of values, and collections can also be thought of as a series of values. The Extend trait bridges this gap, allowing you to extend a collection by including the contents of that iterator. When extending a collection with an already existing key, that entry is updated or, in the case of collections that permit multiple entries with equal keys, that entry is inserted.

Examples

Basic usage:

// You can extend a String with some chars:
let mut message = String::from("The first three letters are: ");

message.extend(&['a', 'b', 'c']);

assert_eq!("abc", &message[29..32]);

Implementing Extend:

// A sample collection, that's just a wrapper over Vec<T>
#[derive(Debug)]
struct MyCollection(Vec<i32>);

// Let's give it some methods so we can create one and add things
// to it.
impl MyCollection {
    fn new() -> MyCollection {
        MyCollection(Vec::new())
    }

    fn add(&mut self, elem: i32) {
        self.0.push(elem);
    }
}

// since MyCollection has a list of i32s, we implement Extend for i32
impl Extend<i32> for MyCollection {

    // This is a bit simpler with the concrete type signature: we can call
    // extend on anything which can be turned into an Iterator which gives
    // us i32s. Because we need i32s to put into MyCollection.
    fn extend<T: IntoIterator<Item=i32>>(&mut self, iter: T) {

        // The implementation is very straightforward: loop through the
        // iterator, and add() each element to ourselves.
        for elem in iter {
            self.add(elem);
        }
    }
}

let mut c = MyCollection::new();

c.add(5);
c.add(6);
c.add(7);

// let's extend our collection with three more numbers
c.extend(vec![1, 2, 3]);

// we've added these elements onto the end
assert_eq!("MyCollection([5, 6, 7, 1, 2, 3])", format!("{c:?}"));

Required Methods§

source

fn extend<T>(&mut self, iter: T)where T: IntoIterator<Item = A>,

Extends a collection with the contents of an iterator.

As this is the only required method for this trait, the trait-level docs contain more details.

Examples

Basic usage:

// You can extend a String with some chars:
let mut message = String::from("abc");

message.extend(['d', 'e', 'f'].iter());

assert_eq!("abcdef", &message);

Provided Methods§

source

fn extend_one(&mut self, item: A)

🔬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.

The default implementation does nothing.

Implementors§

source§

impl Extend<char> for String

1.28.0 · source§

impl Extend<()> for ()

1.45.0 · source§

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

1.52.0 · source§

impl Extend<OsString> for OsString

1.4.0 · source§

impl Extend<String> for String

1.2.0 · source§

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

source§

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

1.52.0 · source§

impl<'a> Extend<&'a OsStr> for OsString

1.19.0 · source§

impl<'a> Extend<Cow<'a, str>> for String

1.52.0 · source§

impl<'a> Extend<Cow<'a, OsStr>> for OsString

1.2.0 · source§

impl<'a, K, V, A> Extend<(&'a K, &'a V)> for BTreeMap<K, V, A>where K: Ord + Copy, V: Copy, A: Allocator + Clone,

1.4.0 · source§

impl<'a, K, V, S> Extend<(&'a K, &'a V)> for HashMap<K, V, S>where K: Eq + Hash + Copy, V: Copy, S: BuildHasher,

1.2.0 · source§

impl<'a, T> Extend<&'a T> for BinaryHeap<T>where T: 'a + Ord + Copy,

1.2.0 · source§

impl<'a, T> Extend<&'a T> for LinkedList<T>where T: 'a + Copy,

1.2.0 · source§

impl<'a, T, A> Extend<&'a T> for BTreeSet<T, A>where T: 'a + Ord + Copy, A: Allocator + Clone,

1.2.0 · source§

impl<'a, T, A> Extend<&'a T> for VecDeque<T, A>where T: 'a + Copy, A: Allocator,

1.2.0 · source§

impl<'a, T, A> Extend<&'a T> for Vec<T, A>where T: Copy + 'a, A: Allocator + 'a,

Extend implementation that copies elements out of references before pushing them onto the Vec.

This implementation is specialized for slice iterators, where it uses copy_from_slice to append the entire slice at once.

1.4.0 · source§

impl<'a, T, S> Extend<&'a T> for HashSet<T, S>where T: 'a + Eq + Hash + Copy, S: BuildHasher,

1.56.0 · source§

impl<A, B, ExtendA, ExtendB> Extend<(A, B)> for (ExtendA, ExtendB)where ExtendA: Extend<A>, ExtendB: Extend<B>,

source§

impl<K, V, A> Extend<(K, V)> for BTreeMap<K, V, A>where K: Ord, A: Allocator + Clone,

source§

impl<K, V, S> Extend<(K, V)> for HashMap<K, V, S>where K: Eq + Hash, S: BuildHasher,

Inserts all new key-values from the iterator and replaces values with existing keys with new values returned from the iterator.

source§

impl<P> Extend<P> for PathBufwhere P: AsRef<Path>,

source§

impl<T> Extend<T> for BinaryHeap<T>where T: Ord,

source§

impl<T> Extend<T> for LinkedList<T>

source§

impl<T, A> Extend<T> for BTreeSet<T, A>where T: Ord, A: Allocator + Clone,

source§

impl<T, A> Extend<T> for VecDeque<T, A>where A: Allocator,

source§

impl<T, A> Extend<T> for Vec<T, A>where A: Allocator,

source§

impl<T, S> Extend<T> for HashSet<T, S>where T: Eq + Hash, S: BuildHasher,