ObserverExample

ObserverExample.swift

protocol ActionDoable: AnyObject {
  func doAction(with value: Int)
}

class A: ActionDoable {
  func doAction(with value: Int) {
    print("do from A \(value)")

  }
}
class B: ActionDoable {
  func doAction(with value: Int) {
    print("do from B \(value)")
  }
}

private class Weakifier<T: AnyObject> {
  weak var weakObject: T?
  init(object: T) {
    self.weakObject = object
  }
}

final class Subject {
  private var actionDoable = [Weakifier<AnyObject>]()

  func addObserver(_ observer: ActionDoable) {
    self.actionDoable.append(Weakifier(object: observer))
  }

  func trigger(value: Int) {
    self.actionDoable
      .compactMap { $0.weakObject as? ActionDoable }
      .forEach { $0.doAction(with: value) }
  }
}

let subject = Subject()
let a = A()
let b = B()
subject.addObserver(a)
subject.addObserver(b)
subject.trigger(value: 1)