Struct hashbrown::hash_map::OccupiedEntryRef
source · [−]pub struct OccupiedEntryRef<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone = Global> { /* private fields */ }
Expand description
A view into an occupied entry in a HashMap
.
It is part of the EntryRef
enum.
Implementations
impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> OccupiedEntryRef<'a, 'b, K, Q, V, S, A>
impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> OccupiedEntryRef<'a, 'b, K, Q, V, S, A>
Gets a reference to the key in the entry.
Examples
use hashbrown::HashMap;
let mut map: HashMap<String, u32> = HashMap::new();
map.entry_ref("poneyland").or_insert(12);
assert_eq!(map.entry_ref("poneyland").key(), "poneyland");
Take the ownership of the key and value from the map.
Examples
use hashbrown::HashMap;
use hashbrown::hash_map::EntryRef;
let mut map: HashMap<String, u32> = HashMap::new();
map.entry_ref("poneyland").or_insert(12);
if let EntryRef::Occupied(o) = map.entry_ref("poneyland") {
// We delete the entry from the map.
o.remove_entry();
}
assert_eq!(map.contains_key("poneyland"), false);
Gets a reference to the value in the entry.
Examples
use hashbrown::HashMap;
use hashbrown::hash_map::EntryRef;
let mut map: HashMap<String, u32> = HashMap::new();
map.entry_ref("poneyland").or_insert(12);
if let EntryRef::Occupied(o) = map.entry_ref("poneyland") {
assert_eq!(o.get(), &12);
}
Gets a mutable reference to the value in the entry.
If you need a reference to the OccupiedEntryRef
which may outlive the
destruction of the EntryRef
value, see into_mut
.
Examples
use hashbrown::HashMap;
use hashbrown::hash_map::EntryRef;
let mut map: HashMap<String, u32> = HashMap::new();
map.entry_ref("poneyland").or_insert(12);
assert_eq!(map["poneyland"], 12);
if let EntryRef::Occupied(mut o) = map.entry_ref("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);
Converts the OccupiedEntryRef 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 OccupiedEntryRef
, see get_mut
.
Examples
use hashbrown::HashMap;
use hashbrown::hash_map::EntryRef;
let mut map: HashMap<String, u32> = HashMap::new();
map.entry_ref("poneyland").or_insert(12);
assert_eq!(map["poneyland"], 12);
if let EntryRef::Occupied(o) = map.entry_ref("poneyland") {
*o.into_mut() += 10;
}
assert_eq!(map["poneyland"], 22);
Sets the value of the entry, and returns the entry’s old value.
Examples
use hashbrown::HashMap;
use hashbrown::hash_map::EntryRef;
let mut map: HashMap<String, u32> = HashMap::new();
map.entry_ref("poneyland").or_insert(12);
if let EntryRef::Occupied(mut o) = map.entry_ref("poneyland") {
assert_eq!(o.insert(15), 12);
}
assert_eq!(map["poneyland"], 15);
Takes the value out of the entry, and returns it.
Examples
use hashbrown::HashMap;
use hashbrown::hash_map::EntryRef;
let mut map: HashMap<String, u32> = HashMap::new();
map.entry_ref("poneyland").or_insert(12);
if let EntryRef::Occupied(o) = map.entry_ref("poneyland") {
assert_eq!(o.remove(), 12);
}
assert_eq!(map.contains_key("poneyland"), false);
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.
Panics
Will panic if this OccupiedEntry was created through EntryRef::insert
.
Examples
use hashbrown::hash_map::{EntryRef, HashMap};
use std::rc::Rc;
let mut map: HashMap<Rc<str>, u32> = HashMap::new();
map.insert(Rc::from("Stringthing"), 15);
if let EntryRef::Occupied(entry) = map.entry_ref("Stringthing") {
// Also replace the key with a handle to our other key.
let (old_key, old_value): (Rc<str>, u32) = entry.replace_entry(16);
}
Replaces the key in the hash map with the key used to create this entry.
Panics
Will panic if this OccupiedEntry was created through Entry::insert
.
Examples
use hashbrown::hash_map::{EntryRef, HashMap};
use std::rc::Rc;
let mut map: HashMap<Rc<str>, u32> = HashMap::new();
let mut known_strings: Vec<Rc<str>> = Vec::new();
// Initialise known strings, run program, etc.
reclaim_memory(&mut map, &known_strings);
fn reclaim_memory(map: &mut HashMap<Rc<str>, u32>, known_strings: &[Rc<str>] ) {
for s in known_strings {
if let EntryRef::Occupied(entry) = map.entry_ref(s.as_ref()) {
// Replaces the entry's key with our version of it in `known_strings`.
entry.replace_key();
}
}
}
Provides shared access to the key and owned access to the value of the entry and allows to replace or remove it based on the value of the returned option.
Examples
use hashbrown::HashMap;
use hashbrown::hash_map::EntryRef;
let mut map: HashMap<String, u32> = HashMap::new();
map.insert("poneyland".to_string(), 42);
let entry = match map.entry_ref("poneyland") {
EntryRef::Occupied(e) => {
e.replace_entry_with(|k, v| {
assert_eq!(k, "poneyland");
assert_eq!(v, 42);
Some(v + 1)
})
}
EntryRef::Vacant(_) => panic!(),
};
match entry {
EntryRef::Occupied(e) => {
assert_eq!(e.key(), "poneyland");
assert_eq!(e.get(), &43);
}
EntryRef::Vacant(_) => panic!(),
}
assert_eq!(map["poneyland"], 43);
let entry = match map.entry_ref("poneyland") {
EntryRef::Occupied(e) => e.replace_entry_with(|_k, _v| None),
EntryRef::Vacant(_) => panic!(),
};
match entry {
EntryRef::Vacant(e) => {
assert_eq!(e.key(), "poneyland");
}
EntryRef::Occupied(_) => panic!(),
}
assert!(!map.contains_key("poneyland"));