Enum Entry

pub enum Entry<'a, K, V, S>
where
    K: Hash + Eq + Clone,
    V: Clone,
    S: BuildHasher,
{
    Occupied(OccupiedEntry<'a, K, V, S>),
    Vacant(VacantEntry<'a, K, V, S>),
}

A handle for a key and its associated value.

Performance Note

When using an Entry, the key is only ever hashed once, when you create the Entry. Operations on an Entry will never trigger a rehash, where eg. a contains_key(key) followed by an insert(key, default_value) (the equivalent of Entry::or_insert()) would need to hash the key once for the contains_key and again for the insert. The operations generally perform similarly otherwise.

Variants

Occupied(OccupiedEntry<'a, K, V, S>)

An entry which exists in the map.

Vacant(VacantEntry<'a, K, V, S>)

An entry which doesn’t exist in the map.

Implementations

impl<'a, K, V, S> Entry<'a, K, V, S>

where K: 'a + Hash + Eq + Clone, V: 'a + Clone, S: 'a + BuildHasher,

pub fn or_insert(self, default: V) -> &'a mut V

Insert the default value provided if there was no value already, and return a mutable reference to the value.

pub fn or_insert_with<F>(self, default: F) -> &'a mut V

where F: FnOnce() -> V,

Insert the default value from the provided function if there was no value already, and return a mutable reference to the value.

pub fn or_default(self) -> &'a mut V

where V: Default,

Insert a default value if there was no value already, and return a mutable reference to the value.

pub fn key(&self) -> &K

Get the key for this entry.

pub fn and_modify<F>(self, f: F) -> Self

where F: FnOnce(&mut V),

Call the provided function to modify the value if the value exists.