Ios 从另一个视图控制器访问更新的变量值

我有一个包含三个不同视图控制器的项目：

ViewController（这是用户输入值的地方）、LoadingViewController（加载屏幕）和AnswerViewController（我希望在第一个视图控制器中加载更新值的结果）

以下是ViewController中的代码：

var calculatedRatio: Double?

@IBOutlet weak var boysCountTextField: UITextField!
@IBOutlet weak var girlsCountTextField: UITextField!

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

@IBAction func calculateButtonTapped(sender: UIButton) {
    if boysCountTextField.text != "" && girlsCountTextField.text != "" {
        calculateRatio()
        self.performSegueWithIdentifier("loadingAnswer", sender: self)
    }
}

func calculateRatio() {

    let boysCount = Double(boysCountTextField.text!)!
    let girlsCount = Double(girlsCountTextField.text!)!

    let currentRatio = boysCount / girlsCount

    calculatedRatio = currentRatio
    print(calculatedRatio)

}

如您所见，在这个视图控制器中，我在顶部创建了一个名为

calculatedRatio

的变量，它是一个可选的双精度变量。在同一视图控制器中，一旦按下按钮，它将在底部运行一个名为

calculateRatio（）

的函数，该函数将更新

calculatedRatio

值

我的问题是，我如何能够在我没有直接进入的另一个视图控制器（AnswerViewController）中访问该变量的新值

---

我已经尝试在AnswerViewController中创建ViewController的实例，但是复制变量时使用其初始值（在本例中为nil），而不是

calculateRatio（）给出的新值

函数。

因此，在处理复杂方法时，您希望显示一个作为自己的视图控制器的加载屏幕。我假设您希望在导航堆栈上抛出一个加载屏幕，而不是进行某种模式覆盖是有原因的。我还假设计算必须在第一视图控制器上进行（与加载屏幕相反），并且没有更好的方法将计算从别处提取出来，这是有原因的。你为什么不试试呢？您可以在LoadingViewController中侦听计算是否完成，并将更新值作为对象传递

您可以使用iOS应用程序的委派模式。在这里，我试图解决你的问题。我对输入ViewController类做了一些更改，以实现AnswerViewController的委托

class ViewController: UIViewController,AnswerVCProtocol {
  var calculatedRatio: Double?

  @IBOutlet weak var boysCountTextField: UITextField!
  @IBOutlet weak var girlsCountTextField: UITextField!

  override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
  }

  override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
  }

  @IBAction func calculateButtonTapped(sender: UIButton) {
    if boysCountTextField.text != "" && girlsCountTextField.text != "" {
      calculateRatio()
      self.performSegueWithIdentifier("loadingAnswer", sender: self)
    }
  }

  func calculateRatio() {

    let boysCount = Double(boysCountTextField.text!)!
    let girlsCount = Double(girlsCountTextField.text!)!

    let currentRatio = boysCount / girlsCount

    calculatedRatio = currentRatio
    print(calculatedRatio)

  }

  // MARK: AnswerViewController Delegate

  func getUpdateRadio()-> Double?{
    return self.calculatedRatio
  }

  override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {

    // Please check you identifier as you given in storyboard
    if segue.identifier == "loadingAnswer"{

      let ansVc = segue.destinationViewController as! AnswerViewController

      ansVc.delegate = self

    }

  }


}

这是协议

protocol AnswerVCProtocol{
  func getUpdateRadio()-> Double?
}

现在我猜你的回答是这样的。这里我只展示如何通过委托访问变量

class AnswerViewController: UIViewController {

  var delegate: AnswerVCProtocol?

  override func viewDidLoad() {
    <#code#>
  }
  // To receive update value call this function when you needed
  // Receive Update Value from your Input ViewController
  func updateRadio(){
    if let _ = self.delegate{
     let updateRatio =  delegate?.getUpdateRadio()
    }

  }

}

class AnswerViewController:UIViewController{
var代表：应答协议？
重写func viewDidLoad（）{
}
//要接收更新值，请在需要时调用此函数
//从输入ViewController接收更新值
func updateRadio（）{
如果让uu=self.delegate{
让updateRatio=delegate？.getUpdateRadio（）
}
}
}

概述

声明协议。在这种情况下，

AnswerVCProtocol

确认输入ViewController中的协议

class ViewController: UIViewController,AnswerVCProtocol {
  var calculatedRatio: Double?

  @IBOutlet weak var boysCountTextField: UITextField!
  @IBOutlet weak var girlsCountTextField: UITextField!

  override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
  }

  override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
  }

  @IBAction func calculateButtonTapped(sender: UIButton) {
    if boysCountTextField.text != "" && girlsCountTextField.text != "" {
      calculateRatio()
      self.performSegueWithIdentifier("loadingAnswer", sender: self)
    }
  }

  func calculateRatio() {

    let boysCount = Double(boysCountTextField.text!)!
    let girlsCount = Double(girlsCountTextField.text!)!

    let currentRatio = boysCount / girlsCount

    calculatedRatio = currentRatio
    print(calculatedRatio)

  }

  // MARK: AnswerViewController Delegate

  func getUpdateRadio()-> Double?{
    return self.calculatedRatio
  }

  override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {

    // Please check you identifier as you given in storyboard
    if segue.identifier == "loadingAnswer"{

      let ansVc = segue.destinationViewController as! AnswerViewController

      ansVc.delegate = self

    }

  }


}

---

我该怎么做？-（void）prepareForSegue:（UIStoryboardSegue*）segue sender:（id）sender{if（[[segue identifier]isequaltstring:@“loadingAnswer]”）{LoadingViewController*destinationViewController=[segue destinationViewController]；destinationViewController.calculateratio=self.calculatedRatio}重写func prepareforsgue（segue:UIStoryboardSegue！，sender:AnyObject！）{if（segue.identifier==“loadingAnswer”）{let vc:LoadingViewController=segue！。destinationViewController作为LoadingViewController.calculatedRatio=self.calculatedRatio}您尝试过使用委派吗？