Trait map_trait::map::Map

pub trait Map<'m, K, V: 'm> {
    type GetGuard: Deref<Target = V>;
    fn get<'a, Q: ?Sized>(&'a self, k: &Q) -> Option<Self::GetGuard>
    where
        K: Borrow<Q>,
        Q: Hash + Eq + Ord;
    fn insert(&mut self, k: K, v: V) -> Option<V>;
}

A generic Map trait

Examples

This is a toy example of a map which reexposes an inner map and stores the most recent key and value to be inserted. Because the LastInsertMap implements Map, it can be seamlessly used as a replacement for other maps.

#![allow(incomplete_features)]
#![feature(generic_associated_types)]
use std::borrow::Borrow;
use std::hash::Hash;
use std::collections::HashMap;

use map_trait::map::Map;
struct LastInsertMap<M, K, V> {
    inner_map: M,
    last_key: K,
    last_value: V,
}

impl<'m, K, V, M> LastInsertMap<M, K, V>
where
    K: Copy,
    V: 'm + Copy,
    M: Map<'m, K, V>,
{
    fn new(mut map: M, key: K, value: V) -> Self {
        map.insert(key, value);
        LastInsertMap {
            inner_map: map,
            last_key: key,
            last_value: value,
        }
    }

    fn get_last_insert(&self) -> (&K, &V) {
        (&self.last_key, &self.last_value)
    }
}

impl<'m, K, V, M> Map<'m, K, V> for LastInsertMap<M, K, V>
where
    K: Copy,
    V: 'm + Copy,
    M: Map<'m, K, V>,
{
    type GetGuard<'a> where 'm: 'a = M::GetGuard<'a>;

    #[inline]
    fn get<'a, Q: ?Sized>(&'a self, k: &Q) -> Option<Self::GetGuard<'a>>
    where
        K: Borrow<Q>,
        Q: Hash + Eq + Ord,
    {
        self.inner_map.get(k)
    }

    #[inline]
    fn insert(&mut self, k: K, v: V) -> Option<V> {
        self.last_key = k;
        self.last_value = v;
        self.inner_map.insert(k, v)
    }
}

    let mut map = LastInsertMap::new(HashMap::new(), 0, 1);
    assert_eq!(map.get_last_insert(), (&0, &1));
    assert_eq!(map.get(&0), Some(&1));
    assert_eq!(map.insert(1, 2), None);
    assert_eq!(map.get(&1), Some(&2));
    assert_eq!(map.get_last_insert(), (&1, &2));

Associated Types

type GetGuard: Deref<Target = V>

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Required methods

fn get<'a, Q: ?Sized>(&'a self, k: &Q) -> Option<Self::GetGuard> where
    K: Borrow<Q>,
    Q: Hash + Eq + Ord, 

fn insert(&mut self, k: K, v: V) -> Option<V>

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Implementations on Foreign Types

impl<'m, K, V, S> Map<'m, K, V> for HashMap<K, V, S> where
    K: Hash + Eq,
    V: 'm,
    S: BuildHasher, 

type GetGuard = &'a V

fn get<'a, Q: ?Sized>(&'a self, k: &Q) -> Option<Self::GetGuard> where
    K: Borrow<Q>,
    Q: Hash + Eq, 

fn insert(&mut self, k: K, v: V) -> Option<V>

impl<'m, K, V> Map<'m, K, V> for BTreeMap<K, V> where
    K: Ord,
    V: 'm, 

type GetGuard = &'a V

fn get<'a, Q: ?Sized>(&'a self, k: &Q) -> Option<Self::GetGuard> where
    K: Borrow<Q>,
    Q: Ord, 

fn insert(&mut self, k: K, v: V) -> Option<V>

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Implementors

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