Swift 如何访问ParentViewController的功能

我使用父视图中的goChildViewController函数切换到ChildViewController

class ParentViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    func goChildViewController() {
        DispatchQueue.main.async {
            self.navigationController?.view.layer.add(CATransition().popFromRight(), forKey: nil)
            self.navigationController?.pushViewController(ChildViewController(), animated: false)
        }
    }

    func needToAccessThisFunction() {
        // I need to call this function from ChildViewController
    }

}

我想从ChildViewController访问函数“needToAccessThisFunction”

class ChildViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        //ParentViewController.needToAccessThisFunction()
    }

}

@IBAction func btnTapped(_ sender: Any) {
    if let parent = self.parent as? ViewController { //ViewController is a parent view controller here.
        parent.methodFromChild()
    }
}

我该怎么做呢？

你可以这样做，但这不是个好主意

您的

ChildViewController

现在位于导航堆栈上，因此您可以调用类似以下内容的父函数：

class ChildViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        if let parent = self.navigationController?.viewControllers[0] as? ParentViewController {
            parent.needToAccessThisFunction()
        }
    }
}

---

这假定

ParentViewController

位于堆栈的底部（项

[0]

）

您可以为此使用代理：-

     protocol requiredMethods: class {
           func a()
           func b()
        }

        class FirstVC: UIViewController, requiredMethods {
            func a() {}
            func b() {}


        func goChildViewController() {
                DispatchQueue.main.async {

        let vc = SecondVC()
               vc.delegate = self
               self.navigationController?.view.layer.add(CATransition().popFromRight(), forKey: nil)
                    self.navigationController?.pushViewController(vc, animated: false)
                }
            }

        }

        class SecondVC: UIViewController {
            weak var delegate: requiredMethods?

            // to  call method a() self.delegate?.a())
            // to  call method b() self.delegate?.b())

        }

---

从子视图控制器调用父视图有多种解决方案

class ChildViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        //ParentViewController.needToAccessThisFunction()
    }

}

@IBAction func btnTapped(_ sender: Any) {
    if let parent = self.parent as? ViewController { //ViewController is a parent view controller here.
        parent.methodFromChild()
    }
}

一种是使用

委托

（我强烈建议这样做），这是一个简单的例子

还有一个，通过在子视图控制器中添加下面的代码，您可以直接调用父视图

class ChildViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        //ParentViewController.needToAccessThisFunction()
    }

}

@IBAction func btnTapped(_ sender: Any) {
    if let parent = self.parent as? ViewController { //ViewController is a parent view controller here.
        parent.methodFromChild()
    }
}

在

ViewController

中，您需要声明

func methodFromChild() {
    print("call from child")
}

---

让“孩子”子类化“家长”子类。类ChildViewController:ParentViewController{}