Events
Well, this is the final blog post in the series of communication between objects and for something familiar, events are available in Objective C and Swift too. The equivalent of ActionScript’s EventDispatcher is called NSNotificationCenter. Rather than each display object inheriting the EventDispatcher, the NSNotificationCenter is more like a central hub where notifications pass through.
The terminology in AS [event, dispatch, listener] becomes in ObjC/Swift [notification, post, observer].
Dispatch Event/Post Notification:
ActionScript3:
this.dispatchEvent(new Event(“SomeEvent”));
Objective C:
[[NSNotificationCenter defaultCenter] postNotificationName:@"SomeNotification" object:self];
Swift:
NSNotificationCenter.defaultCenter().postNotificationName("SomeNotification" object:self)
Listen for Event/Observe Notification:
ActionScript3:
this.addEventListener(“SomeEvent”,someListener);
function someListener(event:Event):void {
// handle event here
}
Objective C:
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(someObserver:) name:@"SomeNotification" object:nil];
- (void)someObserver:(NSNotification *)notification {
// handle event here
}
Swift:
NSNotificationCenter.defaultCenter().addObserver(self, selector: "someObserver:", name: SomeNotification, object: nil)
func someObserver(sender: AnyObject) {
}
Remove Event/Remove Observation:
ActionScript3:
this.removeEventListener(“SomeEvent”,someListener);
Objective C:
[[NSNotificationCenter defaultCenter] removeObserver:self name:@”SomeNotification” object:nil]; //alternatively you can remove all observers on this object: [[NSNotificationCenter defaultCenter] removeObserver:self];
Swift:
NSNotificationCenter.defaultCenter().removeObserver(self name: SomeNotification, object: nil) //alternatively you can remove all observers on this object: NSNotificationCenter.defaultCenter().removeObserver(self)
iOS development with Swift - book: https://manning.com/books/ios-development-with-swift video course: https://www.manning.com/livevideo/ios-development-with-swift-lv
Before I forget... 
[…] 2: Actions Part 3: Delegates Part 4: Blocks/Closures And then in Part 5 I’ll come back to talk about our familiar friend […]