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

    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: FnOnce(&mut V),`
1.26.0
[src]

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

# Examples

    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`
1.28.0
[src]

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

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

Formats the value using the given formatter. Read more

## Auto Trait Implementations

### `impl<'a, K, V> Send for Entry<'a, K, V> where
K: Send,
V: Send,`

### `impl<'a, K, V> Sync for Entry<'a, K, V> where
K: Sync,
V: Sync,`

## Blanket Implementations

### `impl<T> From for T`[src]

#### `fn from(t: T) -> T`[src]

Performs the conversion.

### `impl<T, U> TryFrom for T where
U: Into<T>,` [src]

#### `type Error = Infallible`

The type returned in the event of a conversion error.

#### `fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>`[src]

Performs the conversion.

### `impl<T, U> TryInto for T where
U: TryFrom<T>,` [src]

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

The type returned in the event of a conversion error.

#### `fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>`[src]

Performs the conversion.

### `impl<T, U> Into for T where
U: From<T>,` [src]

#### `fn into(self) -> U`[src]

Performs the conversion.

### `impl<T> Borrow for T where
T: ?Sized,` [src]

#### `fn borrow(&self) -> &T`[src]

Immutably borrows from an owned value. Read more

### `impl<T> BorrowMut for T where
T: ?Sized,` [src]

#### `fn borrow_mut(&mut self) -> &mut T`[src]

Mutably borrows from an owned value. Read more

### `impl<T> Any for T where
T: 'static + ?Sized,` [src]

#### `fn type_id(&self) -> TypeId`[src]

Gets the `TypeId` of `self`. Read more

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