Ios 使用委托创建UIViewController

我有一个

ViewController

，它调用一个自定义类

PopOverModal

，并传入它自己和一个子ViewController

class ViewController: UIViewController {
   ...
    @IBAction func testPopOver(_ sender: Any) {
       var childVC = // initialize child view controller with view from storyboard
       var myPopOverModal = PopOverModal(parent: self, child: childVC);
    }
   ...
}

我需要childVC将一些任务委托给PopOverModal

class ChildViewController: UIViewController {
    ...
    weak var delegate: PopOverModal?
    ...
}

class PopOverModal {
    init(parent: UIViewController, child: UIViewController) {        
        child.delegate = self
        child.dismiss(animated: true, completion: nil)
    }
}

PopOverModal的初始值设定项出现错误，因为UIViewController没有属性

委托

于是我做了以下几件事：

protocol PopOverViewController: class {
    weak var delegate: PopOverModal? {get set}
}

class ChildViewController: UIViewController, PopOverViewController {
    ...
    weak var delegate: PopOverModal?
    ...
}

class PopOverModal {
    init(parent: UIViewController, child: PopOverViewController) {        
        child.delegate = self
        child.dismiss(animated: true, completion: nil)
    }
}

但是，现在我得到一个错误，

discouse

不是PopOverViewController的函数

class ViewController: UIViewController {
   ...
    @IBAction func testPopOver(_ sender: Any) {
       var childVC = // initialize child view controller with view from storyboard
       var myPopOverModal = PopOverModal(parent: self, child: childVC);
    }
   ...
}

在确保ChildViewController继承UIViewController的同时，如何访问UIViewController和PopOverViewController的函数和属性

---

我知道我可以创建一个从UIViewController继承并符合PopOverViewController的混合类，并让我的ChildViewController继承它，但是还有其他方法吗？

如果保证

child

将是

ChildViewController

类的实例，那么您可以修改初始值设定项签名，使其接受相应的对象：

init(parent: UIViewController, child: ChildViewController) {        
  child.delegate = self
  child.dismiss(animated: true, completion: nil)
}

如果它可以是任意UIViewController，但

委托

仅在

ChildViewController

的实例中才是实际的，则可以使用类型转换和可选链接或可选绑定：

// Option #1 - optional chaining
init(parent: UIViewController, child: UIViewController) {
  (child as? ChildViewController)?.delegate = self
  child.dismiss(animated: true, completion: nil)
}

// Option #2 - optional binding
init(parent: UIViewController, child: UIViewController) {
  if let child = child as? ChildViewController {
     child.delegate = self
  }
  child.dismiss(animated: true, completion: nil)
}

顺便说一句，使用基于协议的委派被认为是一种最佳实践。下面是一个如何实现的示例：

protocol PopOverDelegate: class {
  // add any methods and properties that the delegate should implement
  func didPressButton()
}

class ChildViewController: UIViewController {
  ...
  weak var delegate: PopOverDelegate?
  ...
  // call delegate methods where you need them
  func onButtonPress() {
    self.delegate?.didPressButton()
  }
}

class PopOverModal: PopOverDelegate {
  init(parent: UIViewController, child: UIViewController) {        
    (child as? ChildViewController)?.delegate = self
    child.dismiss(animated: true, completion: nil)
  }

  // MARK: - delegate methods
  func didPressButton() {
    print(#function)
  }
}