Struct std::collections::hash_map::OccupiedEntry

1.0.0 · source ·
pub struct OccupiedEntry<'a, K: 'a, V: 'a> { /* private fields */ }
Expand description

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

Implementations§

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");
Run
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);
Run

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);
}
Run

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);
Run

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);
Run

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);
Run

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);
Run
source

pub fn replace_entry(self, value: V) -> (K, V)

🔬This is a nightly-only experimental API. (map_entry_replace #44286)

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);
}
Run
🔬This is a nightly-only experimental API. (map_entry_replace #44286)

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();
        }
    }
}
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Trait Implementations§

Formats the value using the given formatter. Read more

Auto Trait Implementations§

Blanket Implementations§

Gets the TypeId of self. Read more
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

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

The type returned in the event of a conversion error.
Performs the conversion.
The type returned in the event of a conversion error.
Performs the conversion.