Struct ObserverWithCondition 

pub struct ObserverWithCondition<E: Event, B: Bundle, M, S: IntoObserverSystem<E, B, M>> { /* private fields */ }

An observer system with run conditions that preserves event type information.

This type is returned by ObserverSystemExt::run_if and allows entity.observe(system.run_if(cond)) to work with compile-time verification that the event implements EntityEvent.

Implementations

impl<E: Event, B: Bundle, M, S: IntoObserverSystem<E, B, M>> ObserverWithCondition<E, B, M, S>

pub fn run_if<C, CM>(self, condition: C) -> Self

where C: SystemCondition<CM>,

Adds another run condition to this observer.

All conditions must return true for the observer to run (AND semantics).

Note: Chained .run_if() calls do not short-circuit — all conditions run every time to maintain correct change detection ticks. If you need short-circuit behavior, use .run_if(a.and(b)), but be aware this may cause stale Changed<T> detection if the second condition is frequently skipped.

Example

world.add_observer(
    on_event
        .run_if(|a: Res<CondA>| a.0)
        .run_if(|b: Res<CondB>| b.0)
);