Observable, Subscriber Protocols and Extensions in Swift

ObserverProtocol.swift

//
//  ObserverProtocols.swift
//
//  Created by Apro on 18/12/19.
//

import Foundation

protocol Subscriber: class, Hashable {
  associatedtype State
  associatedtype Observable
  var state: State { get set }
  var observable: Observable { get set }
  func update(state: State)
}

protocol Observable: class {
  associatedtype Subscriber: Hashable
  var subscribers: Set<Subscriber> { get set }
  func add(subscriber: Subscriber)
  func remove(subscriber: Subscriber)
}

extension Observable {
  func add(subscriber: Subscriber) {
    subscribers.insert(subscriber)
  }

  func remove(subscriber: Subscriber) {
    subscribers.remove(subscriber)
  }
}

extension Subscriber where State == Int {
  func update(state: Int) {
    self.state = state
  }
}