pub struct OccupiedEntryRef<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone = Global> { /* private fields */ }
Expand description

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

Examples

use hashbrown::hash_map::{EntryRef, HashMap, OccupiedEntryRef};

let mut map = HashMap::new();
map.extend([("a".to_owned(), 10), ("b".into(), 20), ("c".into(), 30)]);

let key = String::from("a");
let _entry_o: OccupiedEntryRef<_, _, _, _> = map.entry_ref(&key).insert(100);
assert_eq!(map.len(), 3);

// Existing key (insert and update)
match map.entry_ref("a") {
    EntryRef::Vacant(_) => unreachable!(),
    EntryRef::Occupied(mut view) => {
        assert_eq!(view.get(), &100);
        let v = view.get_mut();
        *v *= 10;
        assert_eq!(view.insert(1111), 1000);
    }
}

assert_eq!(map["a"], 1111);
assert_eq!(map.len(), 3);

// Existing key (take)
match map.entry_ref("c") {
    EntryRef::Vacant(_) => unreachable!(),
    EntryRef::Occupied(view) => {
        assert_eq!(view.remove_entry(), ("c".to_owned(), 30));
    }
}
assert_eq!(map.get("c"), None);
assert_eq!(map.len(), 2);

Implementations

Gets a reference to the key in the entry.

Examples
use hashbrown::hash_map::{EntryRef, HashMap};

let mut map: HashMap<String, u32> = HashMap::new();
map.entry_ref("poneyland").or_insert(12);

match map.entry_ref("poneyland") {
    EntryRef::Vacant(_) => panic!(),
    EntryRef::Occupied(entry) => assert_eq!(entry.key(), "poneyland"),
}
source

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

Take the ownership of the key and value from the map. Keeps the allocated memory for reuse.

Examples
use hashbrown::HashMap;
use hashbrown::hash_map::EntryRef;

let mut map: HashMap<String, u32> = HashMap::new();
// The map is empty
assert!(map.is_empty() && map.capacity() == 0);

map.entry_ref("poneyland").or_insert(12);
let capacity_before_remove = map.capacity();

if let EntryRef::Occupied(o) = map.entry_ref("poneyland") {
    // We delete the entry from the map.
    assert_eq!(o.remove_entry(), ("poneyland".to_owned(), 12));
}

assert_eq!(map.contains_key("poneyland"), false);
// Now map hold none elements but capacity is equal to the old one
assert!(map.len() == 0 && map.capacity() == capacity_before_remove);

Gets a reference to the value in the entry.

Examples
use hashbrown::HashMap;
use hashbrown::hash_map::EntryRef;

let mut map: HashMap<String, u32> = HashMap::new();
map.entry_ref("poneyland").or_insert(12);

match map.entry_ref("poneyland") {
    EntryRef::Vacant(_) => panic!(),
    EntryRef::Occupied(entry) => assert_eq!(entry.get(), &12),
}

Gets a mutable reference to the value in the entry.

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

Examples
use hashbrown::HashMap;
use hashbrown::hash_map::EntryRef;

let mut map: HashMap<String, u32> = HashMap::new();
map.entry_ref("poneyland").or_insert(12);

assert_eq!(map["poneyland"], 12);
if let EntryRef::Occupied(mut o) = map.entry_ref("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);

Converts the OccupiedEntryRef 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 OccupiedEntryRef, see get_mut.

Examples
use hashbrown::hash_map::{EntryRef, HashMap};

let mut map: HashMap<String, u32> = HashMap::new();
map.entry_ref("poneyland").or_insert(12);

let value: &mut u32;
match map.entry_ref("poneyland") {
    EntryRef::Occupied(entry) => value = entry.into_mut(),
    EntryRef::Vacant(_) => panic!(),
}
*value += 10;

assert_eq!(map["poneyland"], 22);

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

Examples
use hashbrown::HashMap;
use hashbrown::hash_map::EntryRef;

let mut map: HashMap<String, u32> = HashMap::new();
map.entry_ref("poneyland").or_insert(12);

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

assert_eq!(map["poneyland"], 15);

Takes the value out of the entry, and returns it. Keeps the allocated memory for reuse.

Examples
use hashbrown::HashMap;
use hashbrown::hash_map::EntryRef;

let mut map: HashMap<String, u32> = HashMap::new();
// The map is empty
assert!(map.is_empty() && map.capacity() == 0);

map.entry_ref("poneyland").or_insert(12);
let capacity_before_remove = map.capacity();

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

assert_eq!(map.contains_key("poneyland"), false);
// Now map hold none elements but capacity is equal to the old one
assert!(map.len() == 0 && map.capacity() == capacity_before_remove);
source

pub fn replace_entry(self, value: V) -> (K, V)where
    K: From<&'b Q>,

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.

Panics

Will panic if this OccupiedEntry was created through EntryRef::insert.

Examples
use hashbrown::hash_map::{EntryRef, HashMap};
use std::rc::Rc;

let mut map: HashMap<Rc<str>, u32> = HashMap::new();
let key: Rc<str> = Rc::from("Stringthing");

map.insert(key.clone(), 15);
assert_eq!(Rc::strong_count(&key), 2);

match map.entry_ref("Stringthing") {
    EntryRef::Occupied(entry) => {
        let (old_key, old_value): (Rc<str>, u32) = entry.replace_entry(16);
        assert!(Rc::ptr_eq(&key, &old_key) && old_value == 15);
    }
    EntryRef::Vacant(_) => panic!(),
}

assert_eq!(Rc::strong_count(&key), 1);
assert_eq!(map["Stringthing"], 16);

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

Panics

Will panic if this OccupiedEntry was created through Entry::insert.

Examples
use hashbrown::hash_map::{EntryRef, HashMap};
use std::rc::Rc;

let mut map: HashMap<Rc<str>, usize> = HashMap::with_capacity(6);
let mut keys: Vec<Rc<str>> = Vec::with_capacity(6);

for (value, key) in ["a", "b", "c", "d", "e", "f"].into_iter().enumerate() {
    let rc_key: Rc<str> = Rc::from(key);
    keys.push(rc_key.clone());
    map.insert(rc_key.clone(), value);
}

assert!(keys.iter().all(|key| Rc::strong_count(key) == 2));

// It doesn't matter that we kind of use a vector with the same keys,
// because all keys will be newly created from the references
reclaim_memory(&mut map, &keys);

assert!(keys.iter().all(|key| Rc::strong_count(key) == 1));

fn reclaim_memory(map: &mut HashMap<Rc<str>, usize>, keys: &[Rc<str>]) {
    for key in keys {
        if let EntryRef::Occupied(entry) = map.entry_ref(key.as_ref()) {
        /// Replaces the entry's key with our version of it in `keys`.
            entry.replace_key();
        }
    }
}
source

pub fn replace_entry_with<F>(self, f: F) -> EntryRef<'a, 'b, K, Q, V, S, A>where
    F: FnOnce(&Q, V) -> Option<V>,
    K: Borrow<Q>,

Provides shared access to the key and owned access to the value of the entry and allows to replace or remove it based on the value of the returned option.

Examples
use hashbrown::HashMap;
use hashbrown::hash_map::EntryRef;

let mut map: HashMap<String, u32> = HashMap::new();
map.insert("poneyland".to_string(), 42);

let entry = match map.entry_ref("poneyland") {
    EntryRef::Occupied(e) => {
        e.replace_entry_with(|k, v| {
            assert_eq!(k, "poneyland");
            assert_eq!(v, 42);
            Some(v + 1)
        })
    }
    EntryRef::Vacant(_) => panic!(),
};

match entry {
    EntryRef::Occupied(e) => {
        assert_eq!(e.key(), "poneyland");
        assert_eq!(e.get(), &43);
    }
    EntryRef::Vacant(_) => panic!(),
}

assert_eq!(map["poneyland"], 43);

let entry = match map.entry_ref("poneyland") {
    EntryRef::Occupied(e) => e.replace_entry_with(|_k, _v| None),
    EntryRef::Vacant(_) => panic!(),
};

match entry {
    EntryRef::Vacant(e) => {
        assert_eq!(e.key(), "poneyland");
    }
    EntryRef::Occupied(_) => panic!(),
}

assert!(!map.contains_key("poneyland"));

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.