Swift: Determine if the buttons title was changed

问题

Im a newbie in swift, please bear with me.

I have button-A that when clicked show a popover, the popover has a text field and a confirm button. when the confirm is clicked, any value on the text field will be used to change the button-A title.

My question is, how can we monitor if the button title was changed? Obviously We can see it visually but my goal is to do it programatically.

thoughts?

回答1:

An example might help a little here. If a button name myButton I can observe those attributes with:

let options = NSKeyValueObservingOptions([.New, .Old, .Initial, .Prior])

self.addObserver(self, forKeyPath: "myButton.titleLabel.text", options: options, context: nil)

// Changes to these properties will trigger a call to:

override func observeValueForKeyPath(keyPath: String!,
    ofObject object: AnyObject!,
    change: NSDictionary!,
    context: CMutableVoidPointer) {

        println("CHANGE OBSERVED: \(change)")
}

来源：https://stackoverflow.com/questions/38989264/swift-determine-if-the-buttons-title-was-changed