iOS_Swift多代理

protocol MOLocationManagerDelegate: NSObjectProtocol {
  func locationUpdate(_ locs:[String])
}

class MOLocationManager {
  static let shared: MOLocationManager = MOLocationManager()
  
  // 1. NSHashTable中的元素可以通过Hashable协议来判断是否相等.
  // 2. NSHashTable中的元素如果是弱引用,对象销毁后会被移除,可以避免循环引用
  private let multiDelegate: NSHashTable<AnyObject> = NSHashTable.weakObjects()
  
  // MARK: - 需要代理们回调的方法
  func locationUpdate() {
    invoke{ $0.locationUpdate(["北京", "海淀"]) }
  }
  
  func add(_ delegate: MOLocationManagerDelegate) {
    multiDelegate.add(delegate)
  }
  
  func remove(_ delegate: MOLocationManagerDelegate) {
    invoke {
      if $0 === delegate as AnyObject {
        multiDelegate.remove($0)
      }
    }
  }
  
  func removeAll() {
    multiDelegate.removeAllObjects()
  }
  
  private func invoke(_ invocation: (MOLocationManagerDelegate) -> Void) {
    for delegate in multiDelegate.allObjects.reversed() {
      invocation(delegate as! MOLocationManagerDelegate)
    }
  }
}