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>

pub fn key(&self) -> &K

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

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

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<K: Debug + Ord, V, '_> Debug for VacantEntry<'_, K, V>

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.