Message Bus or Event Bus or Publish / Subscribe or Subject / Observer Great for decoupling code. Gecko implements this in nsIObserverService and we have our own messaging system for JS <-> Java. It works well.
We fall down when dealing with Java-only communication. We created a multi-listener in Tabs.java with the OnTabsChangedListener and it's not as nice as we'd like: http://mxr.mozilla.org/mozilla-central/source/mobile/android/base/Tabs.java#535 ----- Original Message ----- > My initial response that any generalization of Event Listening is > indistinguishable from an EventBus. Agreed > I'm generally in favour of EventBuses, but would raise two points which have > bitten me in the past: > * if the event bus / generalized listener manager is does not handle > threading, then this leads to a class of threading bugs. I ding Otto for > this reason (here's a PR implementing that behaviour ). > * keeping the wiring separate and away from the implementation. > * some careful thought needs to go into making sure we're not chucking around > undifferentiated/untyped message or data objects. Otto is pretty good for > this, but probably a bit too simple. I don't know. I like easy to create messages. Creating a calss for all message types is Java's way of adding coupling back into an event bus. Boooo Java! > > perhaps it's time to start thinking about consistent use of messaging for > > inter-component communication. > > The new NativeJSObject stuff in the new sendMessageToJava is a good start, > though there is too much registering, deregistering and switching for my > tastes. > My f2f discussions with mfinkle would indicate he's not impressed by more RPC > type implementations. Indeed. Message (event) buses are for messages (events) and not to replicate functions. If you find yourself creating a "return" message (event) you might be using the wrong tool. That said, I'm OK with look into a message bus for the Java-only code. Use moderation. If we see messages (events) being used willy-nilly, we should clamp down. Don't throw away actual valid uses for OO encapsulation, there are so few of them to begin with.
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