std::collections::btree_map::VacantEntry - Rust
Description: API documentation for the Rust `VacantEntry` struct in crate `std`.
Keywords: rust, rustlang, rust-lang, VacantEntry

# 1.0.0[−][src]Struct std::collections::btree_map::VacantEntry

    pub struct VacantEntry<'a, K, V> where
        K: 'a,
        V: 'a,  { /* fields omitted */ }

A view into a vacant entry in a `BTreeMap`. It is part of the `Entry` enum.

## Methods

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

####
ⓘImportant traits for &'_ mut F

### Important traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?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`
`pub fn key(&self) -> &K`1.10.0[src]

Gets a reference to the key that would be used when inserting a value through the VacantEntry.

# Examples

    use std::collections::BTreeMap;

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

#### `pub fn into_key(self) -> K`1.12.0[src]

Take ownership of the key.

# Examples

    use std::collections::BTreeMap;
    use std::collections::btree_map::Entry;

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

    if let Entry::Vacant(v) = map.entry("poneyland") {
        v.into_key();
    }Run

####
ⓘImportant traits for &'_ mut F

### Important traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?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`
`pub fn insert(self, value: V) -> &'a mut V`[src]

Sets the value of the entry with the `VacantEntry`'s key, and returns a mutable reference to it.

# Examples

    use std::collections::BTreeMap;

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

    // count the number of occurrences of letters in the vec
    for x in vec!["a","b","a","c","a","b"] {
        *count.entry(x).or_insert(0) += 1;
    }

    assert_eq!(count["a"], 3);Run

## Trait Implementations

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

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

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

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

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

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

## Blanket Implementations

### `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.

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

Performs the conversion.

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

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

Performs the conversion.

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

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

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

Performs the conversion.

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

####
ⓘImportant traits for &'_ mut F

### Important traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?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`
`fn borrow(&self) -> &T`[src]

Immutably borrows from an owned value. Read more

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

####
ⓘImportant traits for &'_ mut F

### Important traits for &'_ mut F

`impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?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`
`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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