swift - 快速使用委托(delegate)将字符串从一个 View Controller 发送到另一个 View Controller

Question

我试图在 PopupViewController 中单击按钮，并用字符串“svimmelhed,”填充 DagbogsindlaegViewController 中的文本字段。

运行代码时我没有收到任何错误，但当我运行应用程序模拟并按 PopupViewController 类中的“ButtonPressSvimmelhed”时，文本不存在。有没有一个好心的陌生人可以帮助我并告诉我我做错了什么？

代码如下:

import UIKit
import EventKit
class DagbogsindlaegViewController: UIViewController{

    @IBAction func BackToSVC(_ sender: Any){
        self.performSegue(withIdentifier: "BackToSVCSegue", sender: self)
    }

    @IBAction func ToCalenderButtonPress(_ sender: Any) {
        self.performSegue(withIdentifier: "ToCalenderSegue", sender: self)
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        TitleTextField.delegate = self
        DescriptionTextField.delegate = self


        // Do any additional setup after loading the view.
    }

    @IBOutlet weak var TitleTextField: UITextField!
    @IBOutlet weak var DescriptionTextField: UITextField!

    func addEventToCalendar(title: String, description: String?, startDate: Date, endDate: Date, completion: ((_ success: Bool, _ error: NSError?) -> Void)? = nil) {
        let eventStore = EKEventStore()

        eventStore.requestAccess(to: .event, completion: { (granted, error) in
            if (granted) && (error == nil) {
                let event = EKEvent(eventStore: eventStore)
                event.title = title
                event.startDate = startDate
                event.endDate = endDate
                event.notes = description
                event.calendar = eventStore.defaultCalendarForNewEvents
                do {
                    try eventStore.save(event, span: .thisEvent)
                } catch let e as NSError {
                    completion?(false, e)
                    return
                }
                completion?(true, nil)
            } else {
                completion?(false, error as NSError?)
            }
        })
    }

    @IBAction func ButtonPressGemDagbog(_ sender: Any) {
        addEventToCalendar(title: "\(String(describing: TitleTextField.text!))", description: "\(String(describing: DescriptionTextField.text!))", startDate: NSDate() as Date, endDate: NSDate() as Date)
    }

    @IBAction func ButtonPressPopupMenu(_ sender: Any) {
        let popOverVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "PopupViewControllerID") as! PopupViewController
        self.addChild(popOverVC)
        popOverVC.view.frame = self.view.frame
        self.view.addSubview(popOverVC.view)
        popOverVC.didMove(toParent: self)
    }

}

extension DagbogsindlaegViewController : UITextFieldDelegate {
    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        textField.resignFirstResponder()
        return true
    }
}

extension DagbogsindlaegViewController : TextFraPopupDelegate {
    func Symptomer(Svimmelhed: String) {
        TitleTextField.text = Svimmelhed
    }
}

另一个 View Controller :

import UIKit

protocol TextFraPopupDelegate{
    func Symptomer(Svimmelhed: String)
}

class PopupViewController: UIViewController {

    var symptomDelegate: TextFraPopupDelegate?

    override func viewDidLoad() {
        super.viewDidLoad()

        self.showAnimate()
        self.view.backgroundColor = UIColor.black.withAlphaComponent(0.8)
        // Do any additional setup after loading the view.
    }

    @IBAction func ButtonPressBackToDagbogsindlaeg(_ sender: Any) {
        self.removeAnimate()

        //self.view.removeFromSuperview()
    }
    func showAnimate()
    {
        self.view.transform = CGAffineTransform(scaleX: 1.3, y: 1.3)
        self.view.alpha = 0.0;
        UIView.animate(withDuration: 0.25, animations: {
            self.view.alpha = 1.0
            self.view.transform = CGAffineTransform(scaleX: 1.0, y: 1.0)
        });
    }

    func removeAnimate()
    {
        UIView.animate(withDuration: 0.25, animations: {
            self.view.transform = CGAffineTransform(scaleX: 1.3, y: 1.3)
            self.view.alpha = 0.0;
            }, completion:{(finished : Bool)  in
                if (finished)
                {
                    self.view.removeFromSuperview()
                }
        });
    }

    @IBAction func ButtonPressSvimmelhed(_ sender: UIButton) {
         if sender.isSelected {
            sender.isSelected = false
        } else {
            sender.isSelected = true
        }
        symptomDelegate?.Symptomer(Svimmelhed: "Svimmelhed, ")


    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

    }


}

Answer 1

正如评论中提到的，委托(delegate)未设置。

然而，在 Swift 中，有一种更方便的方法将字符串传递回呈现的 View Controller ，即回调闭包。您摆脱了协议(protocol)和设置委托(delegate)的责任

• 删除

<罢工>

<罢工>

protocol TextFraPopupDelegate{
    func Symptomer(Svimmelhed: String)
}

<罢工>

• 在 PopupViewController替换

  var symptomDelegate: TextFraPopupDelegate?
  

  与

  var callback : ((String) -> Void)?
  

  和

  @IBAction func ButtonPressSvimmelhed(_ sender: UIButton) {
       if sender.isSelected {
          sender.isSelected = false
      } else {
          sender.isSelected = true
      }
      symptomDelegate?.Symptomer(Svimmelhed: "Svimmelhed, ")
  }
  

  与

  @IBAction func ButtonPressSvimmelhed(_ sender: UIButton) {
      sender.isSelected.toggle()  
      callback?("Svimmelhed, ")
  }
  

• 在 DagbogsindlaegViewController在ButtonPressPopupMenu添加闭包

  @IBAction func ButtonPressPopupMenu(_ sender: Any) {
      let popOverVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "PopupViewControllerID") as! PopupViewController
      self.addChild(popOverVC)
      popOverVC.view.frame = self.view.frame
      popOverVC.callback = { string in
         self.TitleTextField.text = string
      }
      self.view.addSubview(popOverVC.view)
      popOverVC.didMove(toParent: self)
  }
  

• 最后删除

<罢工>

<罢工>

 extension DagbogsindlaegViewController : TextFraPopupDelegate {
    func Symptomer(Svimmelhed: String) {
        TitleTextField.text = Svimmelhed
    }
}  

<罢工>

注释:

• 语法 (_ success: Bool, _ error: NSError?) -> Void)?已经过时了。自 Swift 3 以来，参数标签消失了，这就足够了: (Bool, NSError?) -> Void)?

• 不要使用NS... Swift 中的类(如果有 native 对应项，例如 Date)

• 请遵守命名约定，以小写字母开头来命名变量和函数/方法。

• 语法 "\(String(describing: TitleTextField.text!))"是双重冗余的。您可以从字符串创建字符串。将其替换为 TitleTextField.text!