ios - Swift 委托(delegate)不调用父函数

Question

我正在尝试获取一个 subview Controller ，它显示在主父 View Controller 底部的 View 容器中。当我按下子项中的按钮时，“从基本 VC 按下按钮”会打印到控制台，但“从主 VC 按下温暖按钮”不会打印到控制台。我需要在主视图 Controller 中调用打印第二条消息的函数。这是相关的BasicViewController代码:

protocol BasicVCDelegate: class {
    func warmButton()
}

class BasicViewController: UIViewController {
    weak var BasicVCDelegate: BasicVCDelegate?

    @IBOutlet weak var warmButton: UIButton!

    @IBAction func warmButton(sender: AnyObject) {
        print("Button pressed from Basic VC")
        BasicVCDelegate?.warmButton()
    }
}

来自 ViewController.swift

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate, BasicVCDelegate {
    override func viewDidLoad() {
        pauseButton.isEnabled = false

        hideAll();
        self.basicContainer.isUserInteractionEnabled = true;
        self.basicContainer.isHidden = false;

        self.timerLabel.text = String("00:00:00");

        eventTable.dataSource = self
        eventTable.delegate = self

        loadEvents(event: "timer start")
        super.viewDidLoad()
    }

    // CREATE SEGUEs
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if let nav = segue.destination as? UINavigationController, let classBasicVC = nav.topViewController as? BasicViewController {
            classBasicVC.BasicVCDelegate = self
        }
    }

    // FUNCTIONS FOR BASIC VIEW CONTROLLER TO REFERENCE
    func warmButton() {
        print("Warm button pressed from main VC")
    }
}

编辑:从下面的每个人看来，ViewController 中的以下代码部分似乎导致了问题(if 语句中的行从未被调用):

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if let nav = segue.destination as? UINavigationController, let classBasicVC = nav.topViewController as? BasicViewController {
        classBasicVC.basicVCDelegate = self
    }
}

这可能是由于我对委托(delegate)和prepareforsegue函数不熟悉。需要帮助弄清楚“if let”之后应该做什么

编辑2:根据一些用户的建议，将上面的代码替换为以下代码(仍然没有到达打印语句):

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if let nav = segue.destination as? BasicViewController, let classBasicVC = nav.basicVCDelegate {
        print("got here!!")
    }
}

最终编辑:感谢您的帮助!经过一番尝试后，以下内容有效(除了当我解决它时变为错误的警告 - 我可以忍受警告)。

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if let nav = segue.destination as? BasicViewController, let classBasicVC = nav as? BasicViewController? {
        classBasicVC?.basicVCDelegate = self
    }
}

Answer 1

应该是这样的，而不是您上次编辑的代码:

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if let classBasicVC = segue.destination as? BasicViewController {
        classBasicVC.basicVCDelegate = self
    }
}