Struct bevy::ecs::system::In

pub struct In<In>(pub In);

Wrapper type to mark a SystemParam as an input.

Systems may take an optional input which they require to be passed to them when they are being run. For FunctionSystems the input may be marked with this In type, but only the first param of a function may be tagged as an input. This also means a system can only have one or zero input parameters.

Examples

Here is a simple example of a system that takes a usize returning the square of it.

use bevy_ecs::prelude::*;

fn main() {
    let mut square_system = IntoSystem::into_system(square);

    let mut world = World::default();
    square_system.initialize(&mut world);
    assert_eq!(square_system.run(12, &mut world), 144);
}

fn square(In(input): In<usize>) -> usize {
    input * input
}

Tuple Fields

0: In