Trait MutableKeys

pub trait MutableKeys {
    type Key;
    type Value;

    // Required methods
    fn get_full_mut2<Q>(
        &mut self,
        key: &Q,
    ) -> Option<(usize, &mut Self::Key, &mut Self::Value)>
       where Q: Hash + Equivalent<Self::Key> + ?Sized;
    fn retain2<F>(&mut self, keep: F)
       where F: FnMut(&mut Self::Key, &mut Self::Value) -> bool;
    fn __private_marker(&self) -> PrivateMarker;
}

Opt-in mutable access to keys.

These methods expose &mut K, mutable references to the key as it is stored in the map. You are allowed to modify the keys in the hashmap if the modifcation does not change the key’s hash and equality.

If keys are modified erronously, you can no longer look them up. This is sound (memory safe) but a logical error hazard (just like implementing PartialEq, Eq, or Hash incorrectly would be).

use this trait to enable its methods for IndexMap.

Required Associated Types

type Key

type Value

Required Methods

fn get_full_mut2<Q>( &mut self, key: &Q, ) -> Option<(usize, &mut Self::Key, &mut Self::Value)>

where Q: Hash + Equivalent<Self::Key> + ?Sized,

Return item index, mutable reference to key and value

fn retain2<F>(&mut self, keep: F)

where F: FnMut(&mut Self::Key, &mut Self::Value) -> bool,

Scan through each key-value pair in the map and keep those where the closure keep returns true.

The elements are visited in order, and remaining elements keep their order.

Computes in O(n) time (average).

fn __private_marker(&self) -> PrivateMarker

This method is not useful in itself – it is there to “seal” the trait for external implementation, so that we can add methods without causing breaking changes.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors

impl<K, V, S> MutableKeys for IndexMap<K, V, S>

where K: Eq + Hash, S: BuildHasher,

Opt-in mutable access to keys.

See MutableKeys for more information.

type Key = K

type Value = V