std::ops::FnMut

Trait std::ops::FnMut

#[lang = "fn_mut"]
pub trait FnMut<Args>: FnOnce<Args> {
    extern "rust-call" fn call_mut(&mut self, args: Args) -> Self::Output;
}

A version of the call operator that takes a mutable receiver.

Examples

Closures that mutably capture variables automatically implement this trait, which allows them to be invoked.

let mut x = 5;
{
    let mut square_x = || x *= x;
    square_x();
}
assert_eq!(x, 25);

Closures can also be passed to higher-level functions through a FnMut parameter (or a FnOnce parameter, which is a supertrait of FnMut).

fn do_twice<F>(mut func: F)
    where F: FnMut()
{
    func();
    func();
}

let mut x: usize = 1;
{
    	          			          		
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