Enum halfbrown::Entry

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pub enum Entry<'a, K, V, const N: usize, S> {
    Occupied(OccupiedEntry<'a, K, V, N, S>),
    Vacant(VacantEntry<'a, K, V, N, S>),
}

Expand description

A view into a single entry in a map, which may either be vacant or occupied.

This enum is constructed from the entry method on HashMap.

Variants§

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Occupied(OccupiedEntry<'a, K, V, N, S>)

An occupied entry.

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Vacant(VacantEntry<'a, K, V, N, S>)

A vacant entry.

Implementations§

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impl<'a, K, V, const N: usize, S> Entry<'a, K, V, N, S>

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pub fn or_insert(self, default: V) -> &'a mut V
where K: Hash, S: BuildHasher,

Ensures a value is in the entry by inserting the default if empty, and returns a mutable reference to the value in the entry.

§Examples

use halfbrown::HashMap;

let mut map: HashMap<&str, u32> = HashMap::new();

map.entry("poneyland").or_insert(3);
assert_eq!(map["poneyland"], 3);

*map.entry("poneyland").or_insert(10) *= 2;
assert_eq!(map["poneyland"], 6);

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pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V
where K: Hash, S: BuildHasher,

Ensures a value is in the entry by inserting the result of the default function if empty, and returns a mutable reference to the value in the entry.

§Examples

use halfbrown::HashMap;

let mut map: HashMap<&str, String> = HashMap::new();
let s = "hoho".to_string();

map.entry("poneyland").or_insert_with(|| s);

assert_eq!(map["poneyland"], "hoho".to_string());

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pub fn key(&self) -> &K

Returns a reference to this entry’s key.

§Examples

use halfbrown::HashMap;

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

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pub fn and_modify<F>(self, f: F) -> Self
where F: FnOnce(&mut V),

Provides in-place mutable access to an occupied entry before any potential inserts into the map.

§Examples

use halfbrown::HashMap;

let mut map: HashMap<&str, u32> = HashMap::new();

map.entry("poneyland")
   .and_modify(|e| { *e += 1 })
   .or_insert(42);
assert_eq!(map["poneyland"], 42);

map.entry("poneyland")
   .and_modify(|e| { *e += 1 })
   .or_insert(42);
assert_eq!(map["poneyland"], 43);

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impl<'a, K, V: Default, const N: usize, S> Entry<'a, K, V, N, S>

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pub fn or_default(self) -> &'a mut V
where K: Hash, S: BuildHasher,

Ensures a value is in the entry by inserting the default value if empty, and returns a mutable reference to the value in the entry.

§Examples

use halfbrown::HashMap;

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

assert_eq!(map["poneyland"], None);