用Swift 将协议（protocol）中的部分方法设计成可选（optional)

方法一.
@objc protocol SomeProtocol {
  func requiredFunc()
  @objc optional func optionalFunc()
}

方法二.
protocol SomeProtocol {
  func requiredFunc()
  func optionalFunc()
}
extension SomeProtocol {
  func optionalFunc() {
    print(“Dumb Implementation”)
  }
}

Class SomeClass: SomeProtocol {
  func requiredFunc() {
    print(“Only need to implement the required”)
  }
}