解除第二个控制器后如何在第一个控制器中调用函数 [英] How to call a function in the first controller after dismissing the second controller

问题描述

我有两个UIViewController，当我单击一个按钮时，它从第一个视图控制器转到第二个.在此之前，我制作了一个UIView动画以移动到另一个地方.关闭第二个View Controller之后，我想将第一个View Controller中的UIView移回原来的位置.但是，当我在关闭第二个View Controller后从第二个View Controller调用一个函数以动画化第一个View Controller中的UIview时，它无法获取UIView的属性，也无法对其进行任何操作.我认为是因为尚未加载第一个UIViewController.那是问题吗?而我该如何解决呢?

I have two UIViewController, when I click a button, it goes from the first view controller to the second one. And before that, I animated a UIView to move to another place. After dismissing the second View Controller, I want to move the UIView in the first view controller back to where it originally was. However, when I call a function from the second View Controller to animate the UIview in the first view controller after dismissing the second one, It could not get the UIView's properties, and cannot do anything with it. I think because the first UIViewController is not loaded yet. Is that the problem? And How should I solve this?

推荐答案

有两种解决方案，您都可以使用快速闭包

There are two solutions you can either use swift closures

class FirstViewController: UIViewController {

      @IBAction func start(_ sender: Any) {
           guard let secondController = self.storyboard?.instantiateViewController(withIdentifier: "SecondController") as? SecondController else { return }
        secondController.callbackClosure = { [weak self] in
            print("Do your stuff")
        }
        self.navigationController?.pushViewController(secondController, animated: true)
       }
}
//----------------------------

class SecondController: UIViewController {

      var callbackClosure: ((Void) -> Void)?

      override func viewWillDisappear(_ animated: Bool) {
         callbackClosure?()
          }
 }

或者您可以使用协议

class FirstViewController: UIViewController {

@IBAction func start(_ sender: Any) {
       guard let secondController = self.storyboard?.instantiateViewController(withIdentifier: "SecondController") as? SecondController else { return }
        secondController.delegate = self
    self.navigationController?.pushViewController(secondController, animated: true)
   }    

}

extension ViewController : ViewControllerSecDelegate {

    func didBackButtonPressed(){
         print("Do your stuff")
    }
}
//--------------------------


protocol SecondControllerDelegate : NSObjectProtocol {
    func didBackButtonPressed()
}

class SecondController: UIViewController {

    weak var delegate: SecondControllerDelegate?

         override func viewWillDisappear(_ animated: Bool) {
              delegate?.didBackButtonPressed()
         }
 }

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