使用popToRootViewController并传递数据

提问者：小点点

使用popToRootViewController并传递数据

我正在申请一个初级开发人员的职位，我有一个非常具体的任务，这已经花了我3天的时间来完成。听起来很容易--将数据传递给RootViewController。我就是这么做的:

1）

   private func userDefaultsToRootController() {
        let input = textField.text!
        defaults.set(input, forKey: "SavedLabel")
        navigationController?.popViewController(animated: true)
    }

私有函数segueToRootViewController（）{let destinationVC=MainScreen1()let input=TextField.text！

  if input == "" { self.navigationController?.popToRootViewController(animated: true) }

  destinationVC.input = input
  navigationController?.pushViewController(destinationVC, animated: true)

}

private func popToNavigationController() {
    let input = textField.text!
    if let rootVC = navigationController?.viewControllers.first as? MainScreen1 {
        rootVC.input = input
    }
    navigationController?.popToRootViewController(animated: true)
}

但这是困难的部分--我收到一封电子邮件，所有这些方法都不够好，我需要使用delegate和closure。我以前做过委托和闭包，但是当我弹出ToRootViewController时，委托方法传递了nil。你能不能至少指出在哪里能找到这方面的信息？

**增加**

有两个视图控制器:初始视图控制器和第二视图控制器。这就是我在初始视图控制器中的内容:

var secondVC = MainScreen2()

override func viewDidLoad() {
        super.viewDidLoad()     
        secondVC.delegate = self
    }

这就是我推SecondViewController的方式

@objc private func buttonTapped(_ sender: CustomButton) {
        
        let nextViewController = MainScreen2()
        navigationController?.pushViewController(nextViewController, animated: true)
                
    }

在SecondViewController中，我得到了这个协议

protocol PassData {
    func transferData(text: String)
}

也是代表:

var delegate: PassData?

这就是我如何回到初始视图控制器

@objc private func buttonTapped(_ sender: CustomButton) {
        
        if let input = textField.text {
            print(input)
            self.delegate?.transferData(text: input)
            self.navigationController?.popToRootViewController(animated: true)
        }
        
    }

回到我实现委托方法的初始视图控制器

extension MainScreen1: PassData {
    func transferData(text: String) {
        print("delegate called")
        label.text = text
        
    }
}

不调用委托。

共1个答案

匿名用户

基于您的编辑:

必须在ButtonTapped中设置委托

@objc private func buttonTapped(_ sender: CustomButton) {
    
    let nextViewController = MainScreen2()
    nextViewController.delegate = self // HERE WHERE YOU SET THE DELEGATE
    navigationController?.pushViewController(nextViewController, animated: true)
            
}

您可以在ViewDidLoad中删除第二个实例和您的代码。那不是你推的例子。

这将为您指明使用委托和完成处理程序的正确方向。

protocol YourDelegateName {
   func passData(data:YourDataType)
}

class SecondViewController: UIViewController {

  var delegate: YourDelegateName?

  func passDataFromSecondViewController(){

     YourCoreDataClass.shared.getCoreData { (yourStringsArray) in
     self.delegate?.passData(data: yourStringsArray)
     self.navigationController?.popToRootViewController(animated: true)
     }
  }

class InitialViewController: UIViewController, YourDelegateName {


   override func viewDidLoad() {
      super.viewDidLoad()
      // or whenever you instantiate your SecondViewController
      let secondViewController = SecondViewController()
      secondViewController.delegate = self //VERY IMPORTANT, MANY MISS THIS 
      self.navigationController?.pushViewController(createVC, animated: true)
    }


   func passData(data:YourDataType){
       //user your data
   }

}


class YourCoreDataClass: NSObject {
    
     static let  shared = YourCoreDataClass()

     func getCoreData (completion: ([String]) -> ()){
        ........... your code 
         let yourStringsArray = [String]() // let's use as example an array of strings
         //when you got the data your want to pass
         completion(yourStringsArray)
      }
}