cat.swift

protocol CatProtocol {
  var name: String { get set }
  func nya() -> String
  mutating func sleep()
  func clone() -> Self
  func cast<T>(to: T.Type) -> T?
}

class Cat : CatProtocol {
  required init() {}
  var name: String = "tama"
  func nya() -> String { return "nyaaaa" }
  func sleep() { print("zzz...") }
  func clone() -> Self {
    return type(of: self).init()
  }
  func cast<T>(to: T.Type) -> T? {
    return self as? T
  }
}

struct AnyCat1 : CatProtocol {
  private var base: CatProtocol

  init(_ x: CatProtocol) {
    base = x
  }
  var name: String {
    get { return base.name }
    set { base.name = newValue }
  }

  func nya() -> String {
    return base.nya()
  }

  mutating func sleep() { base.sleep() }

  func clone() -> AnyCat1 {
    return AnyCat1(base.clone())
  }

  func cast<T>(to: T.Type) -> T? {
    return base.cast(to: to)
  }
}