Struct std::collections::hash_map::OccupiedEntry
pub struct OccupiedEntry<'a, K: 'a, V: 'a> { /* fields omitted */ }
A view into an occupied entry in a HashMap
. It is part of the Entry
enum.
Implementations
impl<'a, K, V> OccupiedEntry<'a, K, V>
pub fn key(&self) -> &K
Gets a reference to the key in the entry.
Examples
use std::collections::HashMap; let mut map: HashMap<&str, u32> = HashMap::new(); map.entry("poneyland").or_insert(12); assert_eq!(map.entry("poneyland").key(), &"poneyland");
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);
pub fn get(&self) -> &V
Gets a reference to the value in the entry.
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.get(), &12); }
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);
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);
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);
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);
pub fn replace_entry(self, value: V) -> (K, V)
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); }
pub fn replace_key(self) -> K
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(); } } }
Trait Implementations
impl<K: Debug, V: Debug> Debug for OccupiedEntry<'_, K, V>
Auto Trait Implementations
impl<'a, K, V> RefUnwindSafe for OccupiedEntry<'a, K, V> where
K: RefUnwindSafe,
V: RefUnwindSafe,
impl<'a, K, V> Unpin for OccupiedEntry<'a, K, V> where
K: Unpin,
impl<'a, K, V> !UnwindSafe for OccupiedEntry<'a, K, V>
Blanket Implementations
impl<T> From<T> for T
pub fn from(t: T) -> T
Performs the conversion.
pub fn into(self) -> U
Performs the conversion.
type Error = Infallible
The type returned in the event of a conversion error.
pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
Performs the conversion.
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
pub fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
Performs the conversion.
© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/collections/hash_map/struct.OccupiedEntry.html