Trait core::ops::IndexMut [−] [src]

pub trait IndexMut<Idx: ?Sized>: Index<Idx> {
    fn index_mut(&mut self, index: Idx) -> &mut Self::Output;
}

The IndexMut trait is used to specify the functionality of indexing operations like arr[idx], when used in a mutable context.

Examples

A trivial implementation of IndexMut. When Foo[Bar] happens, it ends up calling index_mut, and therefore, main prints Indexing!.

use std::ops::{Index, IndexMut}; #[derive(Copy, Clone)] struct Foo; struct Bar; impl Index<Bar> for Foo { type Output = Foo; fn index<'a>(&'a self, _index: Bar) -> &'a Foo { self } } impl IndexMut<Bar> for Foo { fn index_mut<'a>(&'a mut self, _index: Bar) -> &'a mut Foo { println!("Indexing!"); self } } fn main() { &mut Foo[Bar]; } 
use std::ops::{Index, IndexMut};

#[derive(Copy, Clone)]
struct Foo;
struct Bar;

impl Index<Bar> for Foo {
    type Output = Foo;

    fn index<'a>(&'a self, _index: Bar) -> &'a Foo {
        self
    }
}

impl IndexMut<Bar> for Foo {
    fn index_mut<'a>(&'a mut self, _index: Bar) -> &'a mut Foo {
        println!("Indexing!");
        self
    }
}

fn main() {
    &mut Foo[Bar];
}

Required Methods

fn index_mut(&mut self, index: Idx) -> &mut Self::Output

The method for the indexing (Foo[Bar]) operation

Implementors