Struct serde::lib::core::collections::hash_map::OccupiedEntry

1.0.0 · source ·
pub struct OccupiedEntry<'a, K, V>where
    K: 'a,
    V: 'a,
{ base: RustcOccupiedEntry<'a, K, V, Global>, }
Expand description

A view into an occupied entry in a HashMap. It is part of the Entry enum.

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§base: RustcOccupiedEntry<'a, K, V, Global>

Implementations§

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impl<'a, K, V> OccupiedEntry<'a, K, V>

1.10.0 · source

pub fn key(&self) -> &K

Gets a reference to the key in the entry.

Examples
use std::collections::HashMap;

let mut map: HashMap<&str, u32> = HashMap::new();
map.entry("poneyland").or_insert(12);
assert_eq!(map.entry("poneyland").key(), &"poneyland");
1.12.0 · source

pub fn remove_entry(self) -> (K, V)

Take the ownership of the key and value from the map.

Examples
use std::collections::HashMap;
use std::collections::hash_map::Entry;

let mut map: HashMap<&str, u32> = HashMap::new();
map.entry("poneyland").or_insert(12);

if let Entry::Occupied(o) = map.entry("poneyland") {
    // We delete the entry from the map.
    o.remove_entry();
}

assert_eq!(map.contains_key("poneyland"), false);
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pub fn get(&self) -> &V

Gets a reference to the value in the entry.

Examples
use std::collections::HashMap;
use std::collections::hash_map::Entry;

let mut map: HashMap<&str, u32> = HashMap::new();
map.entry("poneyland").or_insert(12);

if let Entry::Occupied(o) = map.entry("poneyland") {
    assert_eq!(o.get(), &12);
}
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pub fn get_mut(&mut self) -> &mut V

Gets a mutable reference to the value in the entry.

If you need a reference to the OccupiedEntry which may outlive the destruction of the Entry value, see into_mut.

Examples
use std::collections::HashMap;
use std::collections::hash_map::Entry;

let mut map: HashMap<&str, u32> = HashMap::new();
map.entry("poneyland").or_insert(12);

assert_eq!(map["poneyland"], 12);
if let Entry::Occupied(mut o) = map.entry("poneyland") {
    *o.get_mut() += 10;
    assert_eq!(*o.get(), 22);

    // We can use the same Entry multiple times.
    *o.get_mut() += 2;
}

assert_eq!(map["poneyland"], 24);
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pub fn into_mut(self) -> &'a mut V

Converts the OccupiedEntry into a mutable reference to the value in the entry with a lifetime bound to the map itself.

If you need multiple references to the OccupiedEntry, see get_mut.

Examples
use std::collections::HashMap;
use std::collections::hash_map::Entry;

let mut map: HashMap<&str, u32> = HashMap::new();
map.entry("poneyland").or_insert(12);

assert_eq!(map["poneyland"], 12);
if let Entry::Occupied(o) = map.entry("poneyland") {
    *o.into_mut() += 10;
}

assert_eq!(map["poneyland"], 22);
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pub fn insert(&mut self, value: V) -> V

Sets the value of the entry, and returns the entry’s old value.

Examples
use std::collections::HashMap;
use std::collections::hash_map::Entry;

let mut map: HashMap<&str, u32> = HashMap::new();
map.entry("poneyland").or_insert(12);

if let Entry::Occupied(mut o) = map.entry("poneyland") {
    assert_eq!(o.insert(15), 12);
}

assert_eq!(map["poneyland"], 15);
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pub fn remove(self) -> V

Takes the value out of the entry, and returns it.

Examples
use std::collections::HashMap;
use std::collections::hash_map::Entry;

let mut map: HashMap<&str, u32> = HashMap::new();
map.entry("poneyland").or_insert(12);

if let Entry::Occupied(o) = map.entry("poneyland") {
    assert_eq!(o.remove(), 12);
}

assert_eq!(map.contains_key("poneyland"), false);
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pub fn replace_entry(self, value: V) -> (K, V)

🔬This is a nightly-only experimental API. (map_entry_replace)

Replaces the entry, returning the old key and value. The new key in the hash map will be the key used to create this entry.

Examples
#![feature(map_entry_replace)]
use std::collections::hash_map::{Entry, HashMap};
use std::rc::Rc;

let mut map: HashMap<Rc<String>, u32> = HashMap::new();
map.insert(Rc::new("Stringthing".to_string()), 15);

let my_key = Rc::new("Stringthing".to_string());

if let Entry::Occupied(entry) = map.entry(my_key) {
    // Also replace the key with a handle to our other key.
    let (old_key, old_value): (Rc<String>, u32) = entry.replace_entry(16);
}
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pub fn replace_key(self) -> K

🔬This is a nightly-only experimental API. (map_entry_replace)

Replaces the key in the hash map with the key used to create this entry.

Examples
#![feature(map_entry_replace)]
use std::collections::hash_map::{Entry, HashMap};
use std::rc::Rc;

let mut map: HashMap<Rc<String>, u32> = HashMap::new();
let known_strings: Vec<Rc<String>> = Vec::new();

// Initialise known strings, run program, etc.

reclaim_memory(&mut map, &known_strings);

fn reclaim_memory(map: &mut HashMap<Rc<String>, u32>, known_strings: &[Rc<String>] ) {
    for s in known_strings {
        if let Entry::Occupied(entry) = map.entry(Rc::clone(s)) {
            // Replaces the entry's key with our version of it in `known_strings`.
            entry.replace_key();
        }
    }
}

Trait Implementations§

1.12.0 · source§

impl<K, V> Debug for OccupiedEntry<'_, K, V>where
    K: Debug,
    V: Debug,

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

Formats the value using the given formatter. Read more

Auto Trait Implementations§

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impl<'a, K, V> RefUnwindSafe for OccupiedEntry<'a, K, V>where
    K: RefUnwindSafe,
    V: RefUnwindSafe,

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impl<'a, K, V> Send for OccupiedEntry<'a, K, V>where
    K: Send,
    V: Send,

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impl<'a, K, V> Sync for OccupiedEntry<'a, K, V>where
    K: Sync,
    V: Sync,

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impl<'a, K, V> Unpin for OccupiedEntry<'a, K, V>where
    K: Unpin,

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impl<'a, K, V> !UnwindSafe for OccupiedEntry<'a, K, V>

Blanket Implementations§

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impl<T> Any for Twhere
    T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for Twhere
    T: ?Sized,

const: unstable · source§

fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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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
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impl<T> From<T> for T

const: unstable · source§

fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for Twhere
    U: From<T>,

const: unstable · source§

fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T, U> TryFrom<U> for Twhere
    U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
const: unstable · source§

fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for Twhere
    U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
const: unstable · source§

fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.