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

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

    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]

#### `fn key(&self) -> &K`
1.10.0

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");

#### `fn into_key(self) -> K`
1.12.0

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();
    }

#### `fn insert(self, value: V) -> &'a mut V`

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

#### `fn fmt(&self, f: &mut Formatter) -> Result<(), Error>`

Formats the value using the given formatter.

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