Observers swift

Observer.swift

import Foundation

public protocol Observable : class {
	typealias ObserverType
	func addObserver(observer : ObserverType)
	func removeObserver(observer : ObserverType)
}

let observersAssociatedKey = "observersKey"

extension Observable {

	private var observers : NSHashTable  {
		get {
			if let observers = objc_getAssociatedObject(self, observersAssociatedKey) as? NSHashTable {
				return observers
			} else {
				let observers = NSHashTable.weakObjectsHashTable()
				objc_setAssociatedObject(self, observersAssociatedKey, observers, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
				return observers
			}
		}
	}

	public func addObserver(observer : ObserverType) {
		observers.addObject(observer as? AnyObject)
	}

	public func removeObserver(observer : ObserverType) {
		observers.removeObject(observer as? AnyObject)
	}

	public func notifyObservers(notify : (ObserverType) -> ()) {
		for observer in observers.allObjects {
			notify(observer as! ObserverType)
		}
	}
}

public protocol SubjectObserver : AnyObject {
	func subjectDidSomething()
}

public protocol Subject : Observable {
	typealias ObserverType = SubjectObserver
}

public class ConcreteSubject : Subject {
	public func doSomething() {
		notifyObservers { (observer) -> () in
			observer.subjectDidSomething()
		}
	}
}

public class ConcreteObserver : SubjectObserver {
	public func subjectDidSomething() {

	}
}