TargetAction.swift

//: Playground - noun: a place where people can play

import Foundation

// Use of the protocol allows us to hold collections of ActionTrampolices of any type T
protocol Action {
    func performAction() -> Bool
}

class ActionTrampoline<T: AnyObject>: NSObject, Action
{
    weak var target: T?
    var action: (T) -> Void
    
    init(target: T?, action: @escaping (T) -> Void) {
        self.target = target
        self.action = action
    }
    
    @objc func performAction() -> Bool {
        guard let target = target else { return false }
        action(target)
        return true
    }
}

class Target {
    
    var actions = [Action]()
    
    func addObserver<T: AnyObject> (_ target: T?, action: @escaping (T) -> Void) {
        let action = ActionTrampoline (target: target, action: action)
        actions.append(action)
    }
    
    func broadcast() {
        for action in actions {
            action.performAction()
        }
    }
}

class Foo: NSObject {
    func print (_ msg: String) {
        Swift.print (msg)
    }
}



let target = Target()
var foo: Foo? = Foo()

//target.addObserver(Foo) { f in
//    f.print ("got it")
//}

let action = ActionTrampoline(target: foo) { (f) in
    f.print("Got it")
    Swift.print ("Hello")
}

action.performAction()

target.addObserver(foo) { (f) in
    f.print("Got another \(type (of:f))")
    Swift.print ("Hello")
}

let nsstr: NSString = "George"

target.addObserver(nsstr) {
    Swift.print ("String it \($0.lowercased)")
}

//foo = nil
target.broadcast()

//Swift.print ("Hello")