pub struct OccupiedEntry<'a, K, V, S = BuildHasherDefault<AHasher>, A = Global>
where A: Allocator,
{ /* private fields */ }
Expand description

A view into an occupied entry in a HashMap. It is part of the Entry enum.

§Examples

use hashbrown::hash_map::{Entry, HashMap, OccupiedEntry};

let mut map = HashMap::new();
map.extend([("a", 10), ("b", 20), ("c", 30)]);

let _entry_o: OccupiedEntry<_, _, _> = map.entry("a").insert(100);
assert_eq!(map.len(), 3);

// Existing key (insert and update)
match map.entry("a") {
    Entry::Vacant(_) => unreachable!(),
    Entry::Occupied(mut view) => {
        assert_eq!(view.get(), &100);
        let v = view.get_mut();
        *v *= 10;
        assert_eq!(view.insert(1111), 1000);
    }
}

assert_eq!(map[&"a"], 1111);
assert_eq!(map.len(), 3);

// Existing key (take)
match map.entry("c") {
    Entry::Vacant(_) => unreachable!(),
    Entry::Occupied(view) => {
        assert_eq!(view.remove_entry(), ("c", 30));
    }
}
assert_eq!(map.get(&"c"), None);
assert_eq!(map.len(), 2);

Implementations§

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impl<'a, K, V, S, A> OccupiedEntry<'a, K, V, S, A>
where A: Allocator,

pub fn key(&self) -> &K

Gets a reference to the key in the entry.

§Examples
use hashbrown::hash_map::{Entry, HashMap};

let mut map: HashMap<&str, u32> = HashMap::new();
map.entry("poneyland").or_insert(12);

match map.entry("poneyland") {
    Entry::Vacant(_) => panic!(),
    Entry::Occupied(entry) => assert_eq!(entry.key(), &"poneyland"),
}

pub fn remove_entry(self) -> (K, V)

Take the ownership of the key and value from the map. Keeps the allocated memory for reuse.

§Examples
use hashbrown::HashMap;
use hashbrown::hash_map::Entry;

let mut map: HashMap<&str, u32> = HashMap::new();
// The map is empty
assert!(map.is_empty() && map.capacity() == 0);

map.entry("poneyland").or_insert(12);

if let Entry::Occupied(o) = map.entry("poneyland") {
    // We delete the entry from the map.
    assert_eq!(o.remove_entry(), ("poneyland", 12));
}

assert_eq!(map.contains_key("poneyland"), false);
// Now map hold none elements
assert!(map.is_empty());

pub fn get(&self) -> &V

Gets a reference to the value in the entry.

§Examples
use hashbrown::HashMap;
use hashbrown::hash_map::Entry;

let mut map: HashMap<&str, u32> = HashMap::new();
map.entry("poneyland").or_insert(12);

match map.entry("poneyland") {
    Entry::Vacant(_) => panic!(),
    Entry::Occupied(entry) => assert_eq!(entry.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 hashbrown::HashMap;
use hashbrown::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 hashbrown::hash_map::{Entry, HashMap};

let mut map: HashMap<&str, u32> = HashMap::new();
map.entry("poneyland").or_insert(12);

assert_eq!(map["poneyland"], 12);

let value: &mut u32;
match map.entry("poneyland") {
    Entry::Occupied(entry) => value = entry.into_mut(),
    Entry::Vacant(_) => panic!(),
}
*value += 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 hashbrown::HashMap;
use hashbrown::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. Keeps the allocated memory for reuse.

§Examples
use hashbrown::HashMap;
use hashbrown::hash_map::Entry;

let mut map: HashMap<&str, u32> = HashMap::new();
// The map is empty
assert!(map.is_empty() && map.capacity() == 0);

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);
// Now map hold none elements
assert!(map.is_empty());

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.

§Panics

Will panic if this OccupiedEntry was created through Entry::insert.

§Examples
 use hashbrown::hash_map::{Entry, HashMap};
 use std::rc::Rc;

 let mut map: HashMap<Rc<String>, u32> = HashMap::new();
 let key_one = Rc::new("Stringthing".to_string());
 let key_two = Rc::new("Stringthing".to_string());

 map.insert(key_one.clone(), 15);
 assert!(Rc::strong_count(&key_one) == 2 && Rc::strong_count(&key_two) == 1);

 match map.entry(key_two.clone()) {
     Entry::Occupied(entry) => {
         let (old_key, old_value): (Rc<String>, u32) = entry.replace_entry(16);
         assert!(Rc::ptr_eq(&key_one, &old_key) && old_value == 15);
     }
     Entry::Vacant(_) => panic!(),
 }

 assert!(Rc::strong_count(&key_one) == 1 && Rc::strong_count(&key_two) == 2);
 assert_eq!(map[&"Stringthing".to_owned()], 16);

pub fn replace_key(self) -> K

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::{Entry, HashMap};
use std::rc::Rc;

let mut map: HashMap<Rc<String>, usize> = HashMap::with_capacity(6);
let mut keys_one: Vec<Rc<String>> = Vec::with_capacity(6);
let mut keys_two: Vec<Rc<String>> = Vec::with_capacity(6);

for (value, key) in ["a", "b", "c", "d", "e", "f"].into_iter().enumerate() {
    let rc_key = Rc::new(key.to_owned());
    keys_one.push(rc_key.clone());
    map.insert(rc_key.clone(), value);
    keys_two.push(Rc::new(key.to_owned()));
}

assert!(
    keys_one.iter().all(|key| Rc::strong_count(key) == 2)
        && keys_two.iter().all(|key| Rc::strong_count(key) == 1)
);

reclaim_memory(&mut map, &keys_two);

assert!(
    keys_one.iter().all(|key| Rc::strong_count(key) == 1)
        && keys_two.iter().all(|key| Rc::strong_count(key) == 2)
);

fn reclaim_memory(map: &mut HashMap<Rc<String>, usize>, keys: &[Rc<String>]) {
    for key in keys {
        if let Entry::Occupied(entry) = map.entry(key.clone()) {
        // Replaces the entry's key with our version of it in `keys`.
            entry.replace_key();
        }
    }
}

pub fn replace_entry_with<F>(self, f: F) -> Entry<'a, K, V, S, A>
where F: FnOnce(&K, V) -> Option<V>,

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::Entry;

let mut map: HashMap<&str, u32> = HashMap::new();
map.insert("poneyland", 42);

let entry = match map.entry("poneyland") {
    Entry::Occupied(e) => {
        e.replace_entry_with(|k, v| {
            assert_eq!(k, &"poneyland");
            assert_eq!(v, 42);
            Some(v + 1)
        })
    }
    Entry::Vacant(_) => panic!(),
};

match entry {
    Entry::Occupied(e) => {
        assert_eq!(e.key(), &"poneyland");
        assert_eq!(e.get(), &43);
    }
    Entry::Vacant(_) => panic!(),
}

assert_eq!(map["poneyland"], 43);

let entry = match map.entry("poneyland") {
    Entry::Occupied(e) => e.replace_entry_with(|_k, _v| None),
    Entry::Vacant(_) => panic!(),
};

match entry {
    Entry::Vacant(e) => {
        assert_eq!(e.key(), &"poneyland");
    }
    Entry::Occupied(_) => panic!(),
}

assert!(!map.contains_key("poneyland"));

Trait Implementations§

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impl<K, V, S, A> Debug for OccupiedEntry<'_, K, V, S, A>
where K: Debug, V: Debug, A: Allocator,

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fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more
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impl<K, V, S, A> Send for OccupiedEntry<'_, K, V, S, A>
where K: Send, V: Send, S: Send, A: Send + Allocator,

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impl<K, V, S, A> Sync for OccupiedEntry<'_, K, V, S, A>
where K: Sync, V: Sync, S: Sync, A: Sync + Allocator,

Auto Trait Implementations§

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impl<'a, K, V, S, A> RefUnwindSafe for OccupiedEntry<'a, K, V, S, A>

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impl<'a, K, V, S, A> Unpin for OccupiedEntry<'a, K, V, S, A>
where K: Unpin,

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impl<'a, K, V, S = BuildHasherDefault<AHasher>, A = Global> !UnwindSafe for OccupiedEntry<'a, K, V, S, A>

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> Conv for T

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fn conv<T>(self) -> T
where Self: Into<T>,

Converts self into T using Into<T>. Read more
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impl<T> FmtForward for T

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fn fmt_binary(self) -> FmtBinary<Self>
where Self: Binary,

Causes self to use its Binary implementation when Debug-formatted.
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fn fmt_display(self) -> FmtDisplay<Self>
where Self: Display,

Causes self to use its Display implementation when Debug-formatted.
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fn fmt_lower_exp(self) -> FmtLowerExp<Self>
where Self: LowerExp,

Causes self to use its LowerExp implementation when Debug-formatted.
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fn fmt_lower_hex(self) -> FmtLowerHex<Self>
where Self: LowerHex,

Causes self to use its LowerHex implementation when Debug-formatted.
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fn fmt_octal(self) -> FmtOctal<Self>
where Self: Octal,

Causes self to use its Octal implementation when Debug-formatted.
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fn fmt_pointer(self) -> FmtPointer<Self>
where Self: Pointer,

Causes self to use its Pointer implementation when Debug-formatted.
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fn fmt_upper_exp(self) -> FmtUpperExp<Self>
where Self: UpperExp,

Causes self to use its UpperExp implementation when Debug-formatted.
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fn fmt_upper_hex(self) -> FmtUpperHex<Self>
where Self: UpperHex,

Causes self to use its UpperHex implementation when Debug-formatted.
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fn fmt_list(self) -> FmtList<Self>
where &'a Self: for<'a> IntoIterator,

Formats each item in a sequence. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> Pipe for T
where T: ?Sized,

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fn pipe<R>(self, func: impl FnOnce(Self) -> R) -> R
where Self: Sized,

Pipes by value. This is generally the method you want to use. Read more
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fn pipe_ref<'a, R>(&'a self, func: impl FnOnce(&'a Self) -> R) -> R
where R: 'a,

Borrows self and passes that borrow into the pipe function. Read more
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fn pipe_ref_mut<'a, R>(&'a mut self, func: impl FnOnce(&'a mut Self) -> R) -> R
where R: 'a,

Mutably borrows self and passes that borrow into the pipe function. Read more
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fn pipe_borrow<'a, B, R>(&'a self, func: impl FnOnce(&'a B) -> R) -> R
where Self: Borrow<B>, B: 'a + ?Sized, R: 'a,

Borrows self, then passes self.borrow() into the pipe function. Read more
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where Self: BorrowMut<B>, B: 'a + ?Sized, R: 'a,

Mutably borrows self, then passes self.borrow_mut() into the pipe function. Read more
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fn pipe_as_ref<'a, U, R>(&'a self, func: impl FnOnce(&'a U) -> R) -> R
where Self: AsRef<U>, U: 'a + ?Sized, R: 'a,

Borrows self, then passes self.as_ref() into the pipe function.
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fn pipe_as_mut<'a, U, R>(&'a mut self, func: impl FnOnce(&'a mut U) -> R) -> R
where Self: AsMut<U>, U: 'a + ?Sized, R: 'a,

Mutably borrows self, then passes self.as_mut() into the pipe function.
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fn pipe_deref<'a, T, R>(&'a self, func: impl FnOnce(&'a T) -> R) -> R
where Self: Deref<Target = T>, T: 'a + ?Sized, R: 'a,

Borrows self, then passes self.deref() into the pipe function.
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fn pipe_deref_mut<'a, T, R>( &'a mut self, func: impl FnOnce(&'a mut T) -> R ) -> R
where Self: DerefMut<Target = T> + Deref, T: 'a + ?Sized, R: 'a,

Mutably borrows self, then passes self.deref_mut() into the pipe function.
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impl<T> Same for T

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type Output = T

Should always be Self
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impl<T> Tap for T

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fn tap(self, func: impl FnOnce(&Self)) -> Self

Immutable access to a value. Read more
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fn tap_mut(self, func: impl FnOnce(&mut Self)) -> Self

Mutable access to a value. Read more
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fn tap_borrow<B>(self, func: impl FnOnce(&B)) -> Self
where Self: Borrow<B>, B: ?Sized,

Immutable access to the Borrow<B> of a value. Read more
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Mutable access to the BorrowMut<B> of a value. Read more
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Immutable access to the AsRef<R> view of a value. Read more
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Mutable access to the AsMut<R> view of a value. Read more
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where Self: DerefMut<Target = T> + Deref, T: ?Sized,

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where Self: Deref<Target = T>, T: ?Sized,

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fn tap_deref_mut_dbg<T>(self, func: impl FnOnce(&mut T)) -> Self
where Self: DerefMut<Target = T> + Deref, T: ?Sized,

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type Error = Infallible

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