谈谈iOS中的多继承与多重代理

protocol Behavior {
 func run()
}
extension Behavior {
 func run() {
  print("Running...")
 }
}

struct Dog: Behavior {}

let myDog = Dog()
myDog.run() // Running...

// MARK: - 闪烁功能
protocol Blinkable {
 func blink()
}
extension Blinkable where Self: UIView {
 func blink() {
  alpha = 1
  
  UIView.animate(
   withDuration: 0.5,
   delay: 0.25,
   options: [.repeat, .autoreverse],
   animations: {
    self.alpha = 0
  })
 }
}

// MARK: - 放大和缩小
protocol Scalable {
 func scale()
}
extension Scalable where Self: UIView {
 func scale() {
  transfORM = .identity
  
  UIView.animate(
   withDuration: 0.5,
   delay: 0.25,
   options: [.repeat, .autoreverse],
   animations: {
    self.transform = CGAffineTransform(scaleX: 1.5, y: 1.5)
  })
 }
}

// MARK: - 添加圆角
protocol CornersRoundable {
 func roundCorners()
}
extension CornersRoundable where Self: UIView {
 func roundCorners() {
  layer.cornerRadius = bounds.width * 0.1
  layer.masksToBounds = true
 }
}

extension UIView: Scalable, Blinkable, CornersRoundable {}

 cyanView.blink()
 cyanView.scale()
 cyanView.roundCorners()

protocol ProtocolA {
  func method()
}

extension ProtocolA {
  func method() {
    print("Method from ProtocolA")
  }
}

protocol ProtocolB {
  func method()
}

extension ProtocolB {
  func method() {
    print("Method from ProtocolB")
  }
}

class MyClass: ProtocolA, ProtocolB {}

protocol MasterOrderDelegate: class {
  func toEat(_ food: String)
}

class masterOrderDelegateManager : MasterOrderDelegate {
  private let multiDelegate: NSHashTable<AnyObject> = NSHashTable.weakObjects()

  init(_ delegates: [MasterOrderDelegate]) {
    delegates.forEach(multiDelegate.add)
  }
  
  // 协议中的方法,可以有多个
  func toEat(_ food: String) {
    invoke { $0.toEat(food) }
  }
  
  // 添加遵守协议的类
  func add(_ delegate: MasterOrderDelegate) {
    multiDelegate.add(delegate)
  }
  
  // 删除指定遵守协议的类
  func remove(_ delegateToRemove: MasterOrderDelegate) {
    invoke {
      if $0 === delegateToRemove as AnyObject {
        multiDelegate.remove($0)
      }
    }
  }
  
  // 删除所有遵守协议的类
  func removeAll() {
    multiDelegate.removeAllObjects()
  }

  // 遍历所有遵守协议的类
  private func invoke(_ invocation: (MasterOrderDelegate) -> Void) {
    for delegate in multiDelegate.allObjects.reversed() {
      invocation(delegate as! MasterOrderDelegate)
    }
  }
}

class Master {
  weak var delegate: MasterOrderDelegate?
  func orderToEat() {
    delegate?.toEat("meat")
  }
}

class Dog {}
extension Dog: MasterOrderDelegate {
  func toEat(_ food: String) {
    print("\(type(of: self)) is eating \(food)")
  }
}

class Cat {}
extension Cat: MasterOrderDelegate {
  func toEat(_ food: String) {
    print("\(type(of: self)) is eating \(food)")
  }
}

let cat = Cat()
let dog = Dog()
let cat1 = Cat()

let master = Master()
// master的delegate是弱引用,所以不能直接赋值
let delegate = masterOrderDelegateManager([cat, dog])
// 添加遵守该协议的类
delegate.add(cat1)
// 删除遵守该协议的类
delegate.remove(dog)

master.delegate = delegate
master.orderToEat()

// 输出
// Cat is eating meat
// Cat is eating meat