alloc::btree_map::Entry - Rust
Description: API documentation for the Rust `Entry` enum in crate `alloc`.
Keywords: rust, rustlang, rust-lang, Entry

# Enum alloc::btree_map::Entry 1.0.0 [−] [src]

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

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 `BTreeMap`.

## Variants

`Vacant(VacantEntry<'a, K, V>)`

A vacant entry.

`Occupied(OccupiedEntry<'a, K, V>)`

An occupied entry.

## Methods

### `impl<'a, K: Ord, V> Entry<'a, K, V>`
[src]

#### `pub fn or_insert(self, default: V) -> &'a mut V`
[src]

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 std::collections::BTreeMap;

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

    assert_eq!(map["poneyland"], 12);

#### `pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V`
[src]

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 std::collections::BTreeMap;

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

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

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

#### `pub fn key(&self) -> &K`
1.10.0
[src]

Returns a reference to this entry's key.

# Examples

    use std::collections::BTreeMap;

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

#### `pub fn and_modify<F>(self, f: F) -> Self where
F: FnMut(&mut V),`
[src]

🔬 This is a nightly-only experimental API. (`entry_and_modify` #44733)

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

# Examples

    #![feature(entry_and_modify)]
    use std::collections::BTreeMap;

    let mut map: BTreeMap<&str, usize> = BTreeMap::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);

### `impl<'a, K: Ord, V: Default> Entry<'a, K, V>`
[src]

#### `pub fn or_default(self) -> &'a mut V`
[src]

🔬 This is a nightly-only experimental API. (`entry_or_default` #44324)

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

    #![feature(entry_or_default)]
    use std::collections::BTreeMap;

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

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

## Trait Implementations

### `impl<'a, K: 'a + Debug + Ord, V: 'a + Debug> Debug for Entry<'a, K, V>`
1.12.0
[src]

#### `fn fmt(&self, f: &mut Formatter) -> Result`
[src]

Formats the value using the given formatter. Read more

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