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

    pub struct VacantEntry<'a, 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: Ord, V> VacantEntry<'a, K, V>`

[src]

####

`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");

####

`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();
    }

####

`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);

## Trait Implementations

###

`impl<'a, K: 'a + Debug + Ord, V: 'a> Debug for VacantEntry<'a, 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 VacantEntry<'a, K, V> where K: Send, V: Send,`

###

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

## Blanket Implementations

###

`impl<T, U> TryFrom for T where T: From<U>,`

[src]

#### `type Error = !`

🔬 This is a nightly-only experimental API. (`try_from` #33417)

The type returned in the event of a conversion error.

####

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

[src]

🔬 This is a nightly-only experimental API. (`try_from` #33417)

Performs the conversion.

###

`impl<T> From for T`

[src]

####

`fn from(t: T) -> T`

[src]

Performs the conversion.

###

`impl<T, U> TryInto for T where U: TryFrom<T>,`

[src]

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

🔬 This is a nightly-only experimental API. (`try_from` #33417)

The type returned in the event of a conversion error.

####

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

[src]

🔬 This is a nightly-only experimental API. (`try_from` #33417)

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 get_type_id(&self) -> TypeId`

[src]

🔬 This is a nightly-only experimental API. (`get_type_id` #27745)

this method will likely be replaced by an associated static

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

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