Function resource_exists_and_equals

pub fn resource_exists_and_equals<T>(
    value: T,
) -> impl FnMut(Option<Res<'_, T>>) -> bool
where
    T: Resource + PartialEq,

Generates a Condition-satisfying closure that returns true if the resource exists and is equal to value.

The condition will return false if the resource does not exist.

Example

app.add_systems(
    // `resource_exists_and_equals` will only return true
    // if the given resource exists and equals the given value
    my_system.run_if(resource_exists_and_equals(Counter(0))),
);

fn my_system(mut counter: ResMut<Counter>) {
    counter.0 += 1;
}

// `Counter` hasn't been added so `my_system` can't run
app.run(&mut world);
world.init_resource::<Counter>();

// `Counter` is `0` so `my_system` can run
app.run(&mut world);
assert_eq!(world.resource::<Counter>().0, 1);

// `Counter` is no longer `0` so `my_system` won't run
app.run(&mut world);
assert_eq!(world.resource::<Counter>().0, 1);