ios - 两个 View Controller 之间的协议(protocol)

Question

我想在两个 View Controller 之间使用协议(protocol)。我尝试过这样的:

protocol ReceivedPhotosDelegate{
    func reloadData()
}

class SecondViewController: UIViewController {
    var recivedDelegate: ReceivedPhotosDelegate?

    override func viewWillAppear(animated: Bool) {
        super.viewWillAppear(animated)
        self.recivedDelegate!.reloadData()
    }
}

第二类:

class ReceivedPhotosViewController: UIViewController,ReceivedPhotosDelegate {

    func reloadData() {
        print("test ok")
    }
}

当我运行此代码时，出现以下错误:

fatal error: unexpectedly found nil while unwrapping an Optional value

对于这一行:

self.recivedDelegate!.reloadData()

如何解决这个问题？

Answer 1

在ReceivedPhotosViewController内，您应该设置receivedDelegate。将以下行添加到 ReceivedPhotosViewController

的 viewDidLoad 或 viewWillAppear 中

secondVC.recivedDelegate = self    //assuming secondVC is instance of SecondViewController

在调用 reloadData 时都进行 nil 检查

if self.recievedDelegate != nil {
    self.recivedDelegate!.reloadData()
}