GroupEventType.OnEntityRemoved is also triggered when replacing a component about entitas HOT 4 CLOSED

The thing about groups (at least as far as I know) they do not really respond to the entity being added/removed but to each individual component.

So in your PlayerSelectActionAttackSytem you replace the position of the entity, therefore triggering all the groups again. In effect the replace triggers the remove event first (since the old position is removed) and then the add event (since the new position is added).

I hope that makes things a little bit clearer and helps you solve the problem.

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An entity is part of a group, when it fulfills the requirements of the matcher. In your case

Group group = pool.GetGroup(Matcher.AllOf(Matcher.PlayerSelectActionAttack, Matcher.Position));
onAdded = group.CreateObserver (GroupEventType.OnEntityAdded);
onRemoved = group.CreateObserver (GroupEventType.OnEntityRemoved);

an entity belongs to a group when it has a PlayerSelectActionAttackComponent and a PositionComponent.
Whenever you replace either of those it will be removed from the group (intentionally), because the idea is to remove the old component (=> entity doesn't match anymore) and the replace it with the new component (=> entity matches again). As a result e.ReplaceXyz will always trigger OnEntityAdded AND OnEntityRemoved

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Btw, AttackPointerController looks like it should be a ReactiveSystem rather than a MonoBehaviour. A ReactiveSystem is using a GroupObserver under the hood, so you don't have to mess with it. If you still want to use GroupObservers don't forget to call observer.ClearCollectedEntities()
You can get the most out of Entitas if you try putting all your logic into dedicated systems doing only one thing.

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Thanks for yours responses

Now, I understand the concept of ReplaceComponent

You can get the most out of Entitas if you try putting all your logic into dedicated systems doing only one thing.

Ok, I will remove all UI Logic and create dedicated systems

Regards

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