Proper priority handling for events with inheritance

[artkoenig]

Given two events class A {...} and class B extends A {...}

and the corresponding subscriptions

@Subscribe(priority = 2)
public void onEvent(A event)

and

@Subscribe(priority = 1)
public void onEvent(B event)

I would expect, that a B event would first be handled by onEvent(A event) and then onEvent(B event), but this is not the case. The priority is not handled properly for class hierarchies.

[Panthaaaa]

I don't think it should work that way, as the object hierarchy has a higher quality of information than the priority given by the annotation. A more specific subscriber should be always called first, as it has the most specific behavior.

Maybe there could be two priorities :

• GlobalPriority which works regardless of the object hierarchy
• Priority which only works within the object hierarchy

[artkoenig]

A more specific subscriber should be always called first, as it has the most specific behavior.

If I look at how overloaded methods should behave in object oriented programming languages - then event A should be called first and then B. The event handling should follow the class hierarchy in top -> bottom manner.

With the priority attribute you should be able to override this behaviour.

[rvullriede]

I just stumbled across the same issue.

I work extensively with event hierarchies and look for a way to pre-process (with priority = Integer.MIN_VALUE) and post-process (with priority = Integer.MAX_VALUES) all events by subscribing to the parent. If a there is a subscriber for a specific event it should be processed between the generic subscribers (priority default(0)) .

Since changing this now is probably not possible (backward compatibility) I vote for the idea to introduce a globalPriority.