Struct std::collections::hash_map::OccupiedEntry
1.0.0 · source · pub struct OccupiedEntry<'a, K: 'a, V: 'a> { /* private fields */ }
Expand description
A view into an occupied entry in a HashMap
.
It is part of the Entry
enum.
Implementations§
source§impl<'a, K, V> OccupiedEntry<'a, K, V>
impl<'a, K, V> OccupiedEntry<'a, K, V>
1.12.0 · sourcepub fn remove_entry(self) -> (K, V)
pub fn remove_entry(self) -> (K, V)
Take the ownership of the key and value from the map.
§Examples
use std::collections::HashMap;
use std::collections::hash_map::Entry;
let mut map: HashMap<&str, u32> = HashMap::new();
map.entry("poneyland").or_insert(12);
if let Entry::Occupied(o) = map.entry("poneyland") {
// We delete the entry from the map.
o.remove_entry();
}
assert_eq!(map.contains_key("poneyland"), false);
Runsourcepub fn get_mut(&mut self) -> &mut V
pub fn get_mut(&mut self) -> &mut V
Gets a mutable reference to the value in the entry.
If you need a reference to the OccupiedEntry
which may outlive the
destruction of the Entry
value, see into_mut
.
§Examples
use std::collections::HashMap;
use std::collections::hash_map::Entry;
let mut map: HashMap<&str, u32> = HashMap::new();
map.entry("poneyland").or_insert(12);
assert_eq!(map["poneyland"], 12);
if let Entry::Occupied(mut o) = map.entry("poneyland") {
*o.get_mut() += 10;
assert_eq!(*o.get(), 22);
// We can use the same Entry multiple times.
*o.get_mut() += 2;
}
assert_eq!(map["poneyland"], 24);
Runsourcepub fn into_mut(self) -> &'a mut V
pub fn into_mut(self) -> &'a mut V
Converts the OccupiedEntry
into a mutable reference to the value in the entry
with a lifetime bound to the map itself.
If you need multiple references to the OccupiedEntry
, see get_mut
.
§Examples
use std::collections::HashMap;
use std::collections::hash_map::Entry;
let mut map: HashMap<&str, u32> = HashMap::new();
map.entry("poneyland").or_insert(12);
assert_eq!(map["poneyland"], 12);
if let Entry::Occupied(o) = map.entry("poneyland") {
*o.into_mut() += 10;
}
assert_eq!(map["poneyland"], 22);
Runsourcepub fn insert(&mut self, value: V) -> V
pub fn insert(&mut self, value: V) -> V
Sets the value of the entry, and returns the entry’s old value.
§Examples
use std::collections::HashMap;
use std::collections::hash_map::Entry;
let mut map: HashMap<&str, u32> = HashMap::new();
map.entry("poneyland").or_insert(12);
if let Entry::Occupied(mut o) = map.entry("poneyland") {
assert_eq!(o.insert(15), 12);
}
assert_eq!(map["poneyland"], 15);
Runsourcepub fn remove(self) -> V
pub fn remove(self) -> V
Takes the value out of the entry, and returns it.
§Examples
use std::collections::HashMap;
use std::collections::hash_map::Entry;
let mut map: HashMap<&str, u32> = HashMap::new();
map.entry("poneyland").or_insert(12);
if let Entry::Occupied(o) = map.entry("poneyland") {
assert_eq!(o.remove(), 12);
}
assert_eq!(map.contains_key("poneyland"), false);
Runsourcepub fn replace_entry(self, value: V) -> (K, V)
🔬This is a nightly-only experimental API. (map_entry_replace
#44286)
pub fn replace_entry(self, value: V) -> (K, V)
map_entry_replace
#44286)Replaces the entry, returning the old key and value. The new key in the hash map will be the key used to create this entry.
§Examples
#![feature(map_entry_replace)]
use std::collections::hash_map::{Entry, HashMap};
use std::rc::Rc;
let mut map: HashMap<Rc<String>, u32> = HashMap::new();
map.insert(Rc::new("Stringthing".to_string()), 15);
let my_key = Rc::new("Stringthing".to_string());
if let Entry::Occupied(entry) = map.entry(my_key) {
// Also replace the key with a handle to our other key.
let (old_key, old_value): (Rc<String>, u32) = entry.replace_entry(16);
}
Runsourcepub fn replace_key(self) -> K
🔬This is a nightly-only experimental API. (map_entry_replace
#44286)
pub fn replace_key(self) -> K
map_entry_replace
#44286)Replaces the key in the hash map with the key used to create this entry.
§Examples
#![feature(map_entry_replace)]
use std::collections::hash_map::{Entry, HashMap};
use std::rc::Rc;
let mut map: HashMap<Rc<String>, u32> = HashMap::new();
let known_strings: Vec<Rc<String>> = Vec::new();
// Initialise known strings, run program, etc.
reclaim_memory(&mut map, &known_strings);
fn reclaim_memory(map: &mut HashMap<Rc<String>, u32>, known_strings: &[Rc<String>] ) {
for s in known_strings {
if let Entry::Occupied(entry) = map.entry(Rc::clone(s)) {
// Replaces the entry's key with our version of it in `known_strings`.
entry.replace_key();
}
}
}
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