ios - 使用展开转场从文本字段传递数据时出现问题

Question

我正在遵循 this 的已接受答案问题，但我在将数据从 ViewControllerB (第二个 View Controller )传递回 ViewController (初始 View Controller )时遇到问题。根据我添加的一些打印语句的输出，我认为 ViewController 的展开发生在 textFieldDidEndEditing 之前。

dataPassed from ViewControllerB: Default passed data
newValue: Default passed data
textFieldDidEndEditing: Pass this back

通过在 ViewControllerB 上创建按钮的导出并设置 dataPassed = textField.text，我能够成功地将数据传递回 ViewController 。我能够让它工作的另一种方法是通过将 unwindToThisController 中的 dataReceived = sourceViewController.dataPassed 更改为 dataReceived = sourceViewController.textField.text功能。但上面提到的已接受答案的发布者似乎没有使用这些解决方法，而且我不确定这些解决方法中的任何一个是否是可以接受的方法。

我使用的是 Xcode 8.2.1 和 Swift 3。

ViewController代码(初始 View Controller )

/* ViewController.swift */
import UIKit

class ViewController: UIViewController {

  var dataReceived: String? {
    willSet {
      print("newValue: " + newValue!)
      labelOne.text = newValue
    }
  }

  @IBOutlet weak var labelOne: UILabel!

  @IBAction func buttonOne(_ sender: UIButton) {
    performSegue(withIdentifier: "viewNext", sender: self)
  }

  override func viewDidLoad() {
    super.viewDidLoad()
    labelOne.text = "Default passed data"
  }

  // Segue ViewController -> ViewControllerB
  override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "viewNext" {
      let viewControllerB = segue.destination as! ViewControllerB
      viewControllerB.dataPassed = labelOne.text
    }
  }

  // Segue ViewController <- ViewControllerB
  @IBAction func unwindToThisControllerWithSegue(sender: UIStoryboardSegue) {
    if let sourceViewController = sender.source as? ViewControllerB {
      print("dataPassed from ViewControllerB: " + sourceViewController.dataPassed!)
      dataReceived = sourceViewController.dataPassed
      //dataReceived = sourceViewController.textField.text
    }
  }

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

}

ViewControllerB 代码(第二个 View Controller )

/* ViewControllerB.swift */
import UIKit

class ViewControllerB: UIViewController, UITextFieldDelegate {

  var dataPassed: String?

  @IBOutlet weak var textField: UITextField!

  override func viewDidLoad() {
    super.viewDidLoad()
    textField.text = dataPassed
    textField.delegate = self
  }

  // Text field delegate methods
  func textFieldShouldReturn(_ textField: UITextField) -> Bool {
    textField.resignFirstResponder()
    return true
  }

  func textFieldDidEndEditing(_ textField: UITextField) {
    print("textFieldDidEndEditing: " + textField.text!)
    dataPassed = textField.text
  }

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

}

Answer 1

我是这个问题的提出者，幸运的是我有该示例项目的备份，这就是我在那里找到的内容。这就是我在第一个 View Controller 中所做的

var displayValue: Double{
    get{
        return NSNumberFormatter().numberFromString(display.text!)!.doubleValue
    }
    set{
        display.text?="\(newValue)"
        typing=false
    }
}
@IBAction func unwind(segue: UIStoryboardSegue){
    let foo = segue.sourceViewController as! viewControllerB
    let a = foo.dataSent
    displayValue = NSNumberFormatter().numberFromString(a!)!.doubleValue
}

并且运行良好。也许如果您可以分享您正在开发的示例项目，我可以明白为什么它不起作用？ :)