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# Objective - Often in games you will want to create chains of systems that modify some event. For example, a chain of damage systems that handle a DamageEvent and modify the underlying value before the health system finally consumes the event. Right now this requires either: * Using a component added to the entity * Consuming and refiring events Neither is ideal when really all we want to do is read the events value, modify it, and write it back. ## Solution - Create an EventMutator class similar to EventReader but with ResMut<T> and iterators that return &mut so that events can be mutated. ## Testing - I replicated all the existing tests for EventReader to make sure behavior was the same (I believe) and added a number of tests specific to testing that 1) events can actually be mutated, and that 2) EventReader sees changes from EventMutator for events it hasn't already seen. ## Migration Guide Users currently using `ManualEventReader` should use `EventCursor` instead. `ManualEventReader` will be removed in Bevy 0.16. Additionally, `Events::get_reader` has been replaced by `Events::get_cursor`. Users currently directly accessing the `Events` resource for mutation should move to `EventMutator` if possible. --------- Co-authored-by: poopy <gonesbird@gmail.com> Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> |
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3d | ||
window | ||
how_to_test_systems.rs |