pub enum EntryRef<'a, 'b, K, Q: ?Sized, V, S, A = Global> where
A: Allocator + Clone, {
Occupied(OccupiedEntryRef<'a, 'b, K, Q, V, S, A>),
Vacant(VacantEntryRef<'a, 'b, K, Q, V, S, A>),
}
Expand description
A view into a single entry in a map, which may either be vacant or occupied, with any borrowed form of the map’s key type.
This enum
is constructed from the entry_ref
method on HashMap
.
Hash
and Eq
on the borrowed form of the map’s key type must match those
for the key type. It also require that key may be constructed from the borrowed
form through the From
trait.
Examples
use hashbrown::hash_map::{EntryRef, HashMap, OccupiedEntryRef};
let mut map = HashMap::new();
map.extend([("a".to_owned(), 10), ("b".into(), 20), ("c".into(), 30)]);
assert_eq!(map.len(), 3);
// Existing key (insert)
let key = String::from("a");
let entry: EntryRef<_, _, _, _> = map.entry_ref(&key);
let _raw_o: OccupiedEntryRef<_, _, _, _> = entry.insert(1);
assert_eq!(map.len(), 3);
// Nonexistent key (insert)
map.entry_ref("d").insert(4);
// Existing key (or_insert)
let v = map.entry_ref("b").or_insert(2);
assert_eq!(std::mem::replace(v, 2), 20);
// Nonexistent key (or_insert)
map.entry_ref("e").or_insert(5);
// Existing key (or_insert_with)
let v = map.entry_ref("c").or_insert_with(|| 3);
assert_eq!(std::mem::replace(v, 3), 30);
// Nonexistent key (or_insert_with)
map.entry_ref("f").or_insert_with(|| 6);
println!("Our HashMap: {:?}", map);
for (key, value) in ["a", "b", "c", "d", "e", "f"].into_iter().zip(1..=6) {
assert_eq!(map[key], value)
}
assert_eq!(map.len(), 6);
Variants
Occupied(OccupiedEntryRef<'a, 'b, K, Q, V, S, A>)
An occupied entry.
Examples
use hashbrown::hash_map::{EntryRef, HashMap};
let mut map: HashMap<_, _> = [("a".to_owned(), 100), ("b".into(), 200)].into();
match map.entry_ref("a") {
EntryRef::Vacant(_) => unreachable!(),
EntryRef::Occupied(_) => { }
}
Vacant(VacantEntryRef<'a, 'b, K, Q, V, S, A>)
A vacant entry.
Examples
use hashbrown::hash_map::{EntryRef, HashMap};
let mut map: HashMap<String, i32> = HashMap::new();
match map.entry_ref("a") {
EntryRef::Occupied(_) => unreachable!(),
EntryRef::Vacant(_) => { }
}
Implementations
sourceimpl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> EntryRef<'a, 'b, K, Q, V, S, A>
impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> EntryRef<'a, 'b, K, Q, V, S, A>
sourcepub fn insert(self, value: V) -> OccupiedEntryRef<'a, 'b, K, Q, V, S, A> where
K: Hash + From<&'b Q>,
S: BuildHasher,
pub fn insert(self, value: V) -> OccupiedEntryRef<'a, 'b, K, Q, V, S, A> where
K: Hash + From<&'b Q>,
S: BuildHasher,
Sets the value of the entry, and returns an OccupiedEntryRef.
Examples
use hashbrown::HashMap;
let mut map: HashMap<String, u32> = HashMap::new();
let entry = map.entry_ref("horseyland").insert(37);
assert_eq!(entry.key(), "horseyland");
sourcepub fn or_insert(self, default: V) -> &'a mut V where
K: Hash + From<&'b Q>,
S: BuildHasher,
pub fn or_insert(self, default: V) -> &'a mut V where
K: Hash + From<&'b Q>,
S: BuildHasher,
Ensures a value is in the entry by inserting the default if empty, and returns a mutable reference to the value in the entry.
Examples
use hashbrown::HashMap;
let mut map: HashMap<String, u32> = HashMap::new();
// nonexistent key
map.entry_ref("poneyland").or_insert(3);
assert_eq!(map["poneyland"], 3);
// existing key
*map.entry_ref("poneyland").or_insert(10) *= 2;
assert_eq!(map["poneyland"], 6);
sourcepub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V where
K: Hash + From<&'b Q>,
S: BuildHasher,
pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V where
K: Hash + From<&'b Q>,
S: BuildHasher,
Ensures a value is in the entry by inserting the result of the default function if empty, and returns a mutable reference to the value in the entry.
Examples
use hashbrown::HashMap;
let mut map: HashMap<String, u32> = HashMap::new();
// nonexistent key
map.entry_ref("poneyland").or_insert_with(|| 3);
assert_eq!(map["poneyland"], 3);
// existing key
*map.entry_ref("poneyland").or_insert_with(|| 10) *= 2;
assert_eq!(map["poneyland"], 6);
sourcepub fn or_insert_with_key<F: FnOnce(&Q) -> V>(self, default: F) -> &'a mut V where
K: Hash + Borrow<Q> + From<&'b Q>,
S: BuildHasher,
pub fn or_insert_with_key<F: FnOnce(&Q) -> V>(self, default: F) -> &'a mut V where
K: Hash + Borrow<Q> + From<&'b Q>,
S: BuildHasher,
Ensures a value is in the entry by inserting, if empty, the result of the default function.
This method allows for generating key-derived values for insertion by providing the default
function a reference to the key that was moved during the .entry_ref(key)
method call.
The reference to the moved key is provided so that cloning or copying the key is
unnecessary, unlike with .or_insert_with(|| ... )
.
Examples
use hashbrown::HashMap;
let mut map: HashMap<String, usize> = HashMap::new();
// nonexistent key
map.entry_ref("poneyland").or_insert_with_key(|key| key.chars().count());
assert_eq!(map["poneyland"], 9);
// existing key
*map.entry_ref("poneyland").or_insert_with_key(|key| key.chars().count() * 10) *= 2;
assert_eq!(map["poneyland"], 18);
sourcepub fn key(&self) -> &Q where
K: Borrow<Q>,
pub fn key(&self) -> &Q where
K: Borrow<Q>,
Returns a reference to this entry’s key.
Examples
use hashbrown::HashMap;
let mut map: HashMap<String, u32> = HashMap::new();
map.entry_ref("poneyland").or_insert(3);
// existing key
assert_eq!(map.entry_ref("poneyland").key(), "poneyland");
// nonexistent key
assert_eq!(map.entry_ref("horseland").key(), "horseland");
sourcepub fn and_modify<F>(self, f: F) -> Self where
F: FnOnce(&mut V),
pub fn and_modify<F>(self, f: F) -> Self where
F: FnOnce(&mut V),
Provides in-place mutable access to an occupied entry before any potential inserts into the map.
Examples
use hashbrown::HashMap;
let mut map: HashMap<String, u32> = HashMap::new();
map.entry_ref("poneyland")
.and_modify(|e| { *e += 1 })
.or_insert(42);
assert_eq!(map["poneyland"], 42);
map.entry_ref("poneyland")
.and_modify(|e| { *e += 1 })
.or_insert(42);
assert_eq!(map["poneyland"], 43);
sourcepub fn and_replace_entry_with<F>(self, f: F) -> Self where
F: FnOnce(&Q, V) -> Option<V>,
K: Borrow<Q>,
pub fn and_replace_entry_with<F>(self, f: F) -> Self where
F: FnOnce(&Q, V) -> Option<V>,
K: Borrow<Q>,
Provides shared access to the key and owned access to the value of an occupied 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();
let entry = map
.entry_ref("poneyland")
.and_replace_entry_with(|_k, _v| panic!());
match entry {
EntryRef::Vacant(e) => {
assert_eq!(e.key(), "poneyland");
}
EntryRef::Occupied(_) => panic!(),
}
map.insert("poneyland".to_string(), 42);
let entry = map
.entry_ref("poneyland")
.and_replace_entry_with(|k, v| {
assert_eq!(k, "poneyland");
assert_eq!(v, 42);
Some(v + 1)
});
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 = map
.entry_ref("poneyland")
.and_replace_entry_with(|_k, _v| None);
match entry {
EntryRef::Vacant(e) => assert_eq!(e.key(), "poneyland"),
EntryRef::Occupied(_) => panic!(),
}
assert!(!map.contains_key("poneyland"));
sourceimpl<'a, 'b, K, Q: ?Sized, V: Default, S, A: Allocator + Clone> EntryRef<'a, 'b, K, Q, V, S, A>
impl<'a, 'b, K, Q: ?Sized, V: Default, S, A: Allocator + Clone> EntryRef<'a, 'b, K, Q, V, S, A>
sourcepub fn or_default(self) -> &'a mut V where
K: Hash + From<&'b Q>,
S: BuildHasher,
pub fn or_default(self) -> &'a mut V where
K: Hash + From<&'b Q>,
S: BuildHasher,
Ensures a value is in the entry by inserting the default value if empty, and returns a mutable reference to the value in the entry.
Examples
use hashbrown::HashMap;
let mut map: HashMap<String, Option<u32>> = HashMap::new();
// nonexistent key
map.entry_ref("poneyland").or_default();
assert_eq!(map["poneyland"], None);
map.insert("horseland".to_string(), Some(3));
// existing key
assert_eq!(map.entry_ref("horseland").or_default(), &mut Some(3));
Trait Implementations
Auto Trait Implementations
impl<'a, 'b, K, Q: ?Sized, V, S, A> RefUnwindSafe for EntryRef<'a, 'b, K, Q, V, S, A> where
A: RefUnwindSafe,
K: RefUnwindSafe,
Q: RefUnwindSafe,
S: RefUnwindSafe,
V: RefUnwindSafe,
impl<'a, 'b, K, Q: ?Sized, V, S, A> Send for EntryRef<'a, 'b, K, Q, V, S, A> where
A: Send,
K: Send,
Q: Sync,
S: Send,
V: Send,
impl<'a, 'b, K, Q: ?Sized, V, S, A> Sync for EntryRef<'a, 'b, K, Q, V, S, A> where
A: Sync,
K: Sync,
Q: Sync,
S: Sync,
V: Sync,
impl<'a, 'b, K, Q: ?Sized, V, S, A> Unpin for EntryRef<'a, 'b, K, Q, V, S, A> where
K: Unpin,
impl<'a, 'b, K, Q, V, S, A = Global> !UnwindSafe for EntryRef<'a, 'b, K, Q, V, S, A>
Blanket Implementations
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more