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

    pub enum Entry<'a, K, V> where
        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.

## Implementations

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

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

### Notable traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W`
`[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);

Run

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

### Notable traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W`
where
F: FnOnce() -> 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());

Run

#### `pub fn or_insert_with_key<F>(self, default: F) -> &'a mut Vⓘ

### Notable traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W`
where
F: FnOnce(&K) -> V,` 1.50.0[src]

Ensures a value is in the entry by inserting, if empty, the result of the default function. This method allows for generating key-derived values for insertion by providing the default function a reference to the key that was moved during the `.entry(key)` method call.

The reference to the moved key is provided so that cloning or copying the key is unnecessary, unlike with `.or_insert_with(|| ... )`.

# Examples

    use std::collections::BTreeMap;

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

    map.entry("poneyland").or_insert_with_key(|key| key.chars().count());

    assert_eq!(map["poneyland"], 9);

Run

#### `pub fn key(&self) -> &Kⓘ

### Notable traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W`
`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");

Run

#### `pub fn and_modify<F>(self, f: F) -> Entry<'a, K, V> 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);

Run

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

#### `pub fn or_default(self) -> &'a mut Vⓘ

### Notable traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W`
`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);

Run

## Trait Implementations

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

#### `pub fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>`[src]

Formats the value using the given formatter. Read more

## Auto Trait Implementations

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

### `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,`

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

### `impl<'a, K, V> !UnwindSafe for Entry<'a, K, V>`

## Blanket Implementations

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

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

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

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

#### `pub fn borrow(&self) -> &Tⓘ

### Notable traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W`
`[src]

Immutably borrows from an owned value. Read more

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

#### `pub fn borrow_mut(&mut self) -> &mut Tⓘ

### Notable traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Future + Unpin + ?Sized, type Output = <F as Future>::Output;impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;impl<R: Read + ?Sized> Read for &mut Rimpl<W: Write + ?Sized> Write for &mut W`
`[src]

Mutably borrows from an owned value. Read more

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

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

Performs the conversion.

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

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

Performs the conversion.

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

#### `type Error = Infallible`

The type returned in the event of a conversion error.

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

Performs the conversion.

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

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

The type returned in the event of a conversion error.

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

Performs the conversion.