我正在尝试使用 setter 和 getter 函数将变量从 subview (inputPopUp.swift) 传递到父 View 。这是我的 subview 中的代码:

var char: String!
var buttonPressed = String()

@IBAction func addButtonPressed(sender: AnyObject) {
    buttonPressed = "addButton"
    setChar("+")
    getChar()
    self.removeAnimate()
}

@IBAction func minusButtonPressed(sender: AnyObject) {
    buttonPressed = "minusButton"
    setChar("-")
    self.removeAnimate()
}

@IBAction func divideButtonPressed(sender: AnyObject) {
    buttonPressed = "divideButton"
    setChar("/")
    self.removeAnimate()
}

@IBAction func multiplyButtonPressed(sender: AnyObject) {
    buttonPressed = "multiplyButton"
    setChar("*")
    self.removeAnimate()
}

//setter method
func setChar(var thisChar: String){
    char = thisChar
}

//getter method
func getChar()-> String{
    if (buttonPressed == "addButton"){
        char = "+"
    }
    if (buttonPressed == "minusButton"){
        char = "-"
    }
    if (buttonPressed == "divideButton"){
        char = "/"
    }
    if (buttonPressed == "multiplyButton"){
        char = "*"
    }
    return char
}

我正尝试像这样访问父 View 中的“char”变量，但它返回 nil - 大概是因为我正在调用该函数的新实例。

@IBAction func runButtonPressed(sender: AnyObject) {
    inputPopUp().getChar()
} 

如何有效地将数据从子级传递给父级？

我还想根据 subview 中的按钮点击更新父 View 中的标签。我正在尝试实现键值观察。这是我到目前为止所得到的。

class ObserveChar: NSObject {

dynamic var char = String()

func updateChar(){

    char = String()
}

private var myContext = 0

class Observer: NSObject {

var objectToObserve = ObserveChar()

override init(){

    super.init()

    objectToObserve.addObserver(self, forKeyPath: "char", options: .New, context: &myContext)
}

override func observeValueForKeyPath(keyPath: String, ofObject object: AnyObject, change: [NSObject : AnyObject], context: UnsafeMutablePointer<Void>) {

    if context == &myContext {

        println("Char updated: \(change[NSKeyValueChangeNewKey])")

    } else {
        super.observeValueForKeyPath(keyPath, ofObject: object, change: change, context: context)
    }
}

deinit {

    objectToObserve.removeObserver(self, forKeyPath: "char", context: &myContext)

}

最佳答案

看来你的项目是关于计算器的。你不应该使用

ParentView().tapLabel.text = getChar() 因为，你已经多次创建了parentView，你应该将parentView设置为它的weak属性

也可以使用KVO观察 subview 的char变量；也可以使用NSNotification更新父 View 的tapLabel；或者也可以使用delegate。 代表喜欢下面

protocol UpdateTapLabel {
func didTapSomeOperateAction(operateInfo : String)

class ParentClass : NSObject, UpdateTapLabel {
var tapLabel : UILabel!
var childView : ChildView!
func didTapSomeOperateAction(operateInfo: String) {
    self.tapLabel.text = operateInfo
}
//you should initialize the child view like this
/*
childView = ChildView()
childView.delegate = self
*/

class ChildView: NSObject {
var char: String!
var delegate : UpdateTapLabel
//getter method
func getChar() {
    if (buttonPressed == "addButton"){
        char = "+"
    }
    if (buttonPressed == "minusButton"){
        char = "-"
    }
    if (buttonPressed == "divideButton"){
        char = "/"
    }
    if (buttonPressed == "multiplyButton"){
        char = "*"
    }
    self.delegate.didTapSomeOperateAction(char)
}

KVO 喜欢下面

//you should add observer like this
//self.addObserver(self, forKeyPath: "childView.char", options: NSKeyValueObservingOptions.New, context: nil)
//also you should remove it in deinit, otherwise you will get crash when release parentView
deinit {
    self.removeObserver(self, forKeyPath: "childView.char")
}
//you can handle the kvo here
override func observeValueForKeyPath(keyPath: String, ofObject object: AnyObject, change: [NSObject : AnyObject], context: UnsafeMutablePointer<Void>) {
    if keyPath == "childView.char" {
        self.tapLabel.text = change[NSKeyValueChangeNewKey]
    }
}

关于swift - 在 Swift 中将变量从 subview 传递到父 View ，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/32097578/