你如何更新你从一个类委托给另一个类的值？

Question

我遇到了委派问题。我对这个概念比较陌生，但从概念上讲，我明白了，它很重要。我只是在使用它时遇到了麻烦。我似乎无法将数据从一个类传递到另一个类。我知道在堆栈溢出方面存在现有的委托示例，但它们并没有完全理解我的误解。我得到了协议的使用，委托，并在一个类中调用它。我相信我只是缺少一些细微的差别......而且它在我的代码中缺乏功能是可见的

//my protocol:

protocol StingHolder {
    func StringPasser(ThisText text: String)
}

创建委托协议关系，放置要传递的数据，然后关闭视图控制器

// my classes for placing data to be passed

class changeLabel: UIViewController,UITextFieldDelegate{

   var Delegate: StingHolder?


    @IBOutlet weak var TexrBeingPassed: UITextField!

    override func viewDidLoad() {
        super.viewDidLoad()

        TexrBeingPassed.delegate = self
        // Do any additional setup after loading the view.
    }



    @IBAction func ButtonPassingDataOtherView(_ sender: Any) {

            Delegate?.StringPasser(ThisText: TexrBeingPassed.text!)
            dismiss(animated: true, completion: nil)


    }
}

创建一个更改标签类及其委托的实例，并将自己设置为委托 *据说会更改标签，但它没有

///class to receive data


class ViewController: UIViewController{
    @IBOutlet weak var LableName: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()

        var lableChange = changeLabel()
        lableChange.Delegate = self

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


    @IBAction func EditController(_ sender: Any) {

        var storyBoard = UIStoryboard(name: "Test", bundle: nil)
        var ViewController = storyBoard.instantiateViewController(withIdentifier: "TestView")
        self.present(ViewController, animated: true, completion: nil)
    }


}

继承协议并告诉它将标签更改为 changelabel 类委托传递的任何内容

// extension view controller inheriting the protocol

extension ViewController : StingHolder{

    func StringPasser(ThisText text: String){

        print("Delegate is working")
        LableName.text = text
        ///
    }  
}

我希望一个视图控制器编辑另一个视图控制器的文本标签

Answer 1

您拥有self 作为委托的对象与屏幕上显示的对象不同。

override func viewDidLoad() {
    super.viewDidLoad()

    // "labelChange.delegate" is set...
    var lableChange = changeLabel()
    lableChange.Delegate = self

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


@IBAction func EditController(_ sender: Any) {

    var storyBoard = UIStoryboard(name: "Test", bundle: nil)
    // but "ViewController" is presented
    var ViewController = storyBoard.instantiateViewController(withIdentifier: "TestView")
    self.present(ViewController, animated: true, completion: nil)
}

labelChange 和 ViewController 是两个不同的独立对象。一个通过直接调用init 创建，另一个通过调用storyBoard.instantiateViewController 创建。您应该改为设置 latter 的委托：

override func viewDidLoad() {
    super.viewDidLoad()

    // "labelChange.delegate" can be deleted
}


@IBAction func EditController(_ sender: Any) {

    var storyBoard = UIStoryboard(name: "Test", bundle: nil)
    if let ViewController = storyBoard.instantiateViewController(withIdentifier: "TestView") as? labelChange {
        ViewController.delegate = self
        self.present(ViewController, animated: true, completion: nil)
    }
}