[Question] What is the point of OnEntityUpdated? about entitas HOT 7 CLOSED

Another possible oddity, for Matchers instead of OnEntityUpdate it's OnEntityAddedOrRemoved. If these methods represent the same functionality they should probably have the same method name.

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I think you're right. In this case we can remove

gameBoardElements.OnEntityUpdated += onGameBoardElementUpdated

since replacing a component will also call OnEntityRemoved and OnEntityAdded. So it's redundant... I'll remove it from the example.

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OnEntityAddedOrRemoved means it triggers when added OR when removed from the group.
To recap:

Adding a component to an entity might result in the entity being added to a group. This will trigger OnEntityAdded

Replacing the component will trigger OnEntityRemoved, OnEntityAdded, OnEntityUpdated

Removing the component will trigger OnEntityRemoved

Usually reactive systems are interested in changes in the group thus triggering OnEntityAdded. In my experience it's a rare case when you actually want to trigger OnEntityAddedOrRemoved, meaning reacting on any change in the group, e.g AccelerateSystem.cs

from entitas.

Makes sense. I appreciate the explanation.

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I noticed OnEntityUpdated not function well when i change value in Unity inspector, when value changed, previousComponent is equals to newComponent.Same as OnEntityRemoved, when OnEntityRemoved's event is called, component's value(string type) has already be changed.I don't know if it is an issue.

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I think you're right. The entity inspector just calls entity.ReplaceComponent() without using the componentPool and providing both the previous and the new component like the generated methods do.
I'll work on a fix.
Thanks for letting me know! :)

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I destroyed my entity than entity's last component removed.
after long testing, I understand the mechanism (casting component Arg to removed component)
this is very confusing...
how about adding simple event?
like

Group.OnEntityRemoved(Entity entity);

have a good day.

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