Trait intrusive_collections::KeyAdapter

source ·

pub trait KeyAdapter<'a>: Adapter {
    type Key;

    // Required method
    fn get_key(
        &self,
        value: &'a <Self::PointerOps as PointerOps>::Value
    ) -> Self::Key;
}

Expand description

Extension of the Adapter trait to provide a way of extracting a key from an object. This key can then be used as an index in certain intrusive collections (currently only RBTree uses this).

The key can be returned either as a value or as a reference, which allows you to

Examples

use intrusive_collections::intrusive_adapter;
use intrusive_collections::{RBTreeLink, KeyAdapter};

struct S {
    link: RBTreeLink,
    key: u32,
    value: u64,
}

// Adapter which returns a key by value
intrusive_adapter!(MyAdapter = Box<S>: S { link : RBTreeLink });
impl<'a> KeyAdapter<'a> for MyAdapter {
    type Key = u32;
    fn get_key(&self, s: &'a S) -> u32 { s.key }
}

// Adapter which returns a key by reference
intrusive_adapter!(MyAdapter2 = Box<S>: S { link : RBTreeLink });
impl<'a> KeyAdapter<'a> for MyAdapter2 {
    type Key = &'a u32;
    fn get_key(&self, s: &'a S) -> &'a u32 { &s.key }
}

struct U {
    link: RBTreeLink,
    key1: i32,
    key2: String,
    key3: f64,
}

// Adapter which returns a tuple as a key. When used in a RBTree, this will
// keep all elements sorted by `key1` first, then `key2` and finally `key3`.
intrusive_adapter!(MyAdapter3 = Box<U>: U { link : RBTreeLink });
impl<'a> KeyAdapter<'a> for MyAdapter3 {
    type Key = (i32, &'a str, f64);
    fn get_key(&self, u: &'a U) -> Self::Key { (u.key1, &u.key2, u.key3) }
}

Required Associated Types§

source

type Key

Type of the key returned by get_key.

Required Methods§