class A:EventSender{
    func doSomething(){
        onEvent(Event(Event.update,self)) 
    }
}
var a = A()
func onSomeEvent(event:Event){/*<--Event handler*/
    if event.assert(.update,origin:a){
        print("something happened on: \(event.origin) for event type: \(event.type)")
    } 
}
a.event = onSomeEvent
a.doSomething()//Output: something happened on: A for event type: eventUpdate