不使用键盘快速键检测何时更改UITextField

Question

I would like to know when the "text" property of myTextField, which is a subclass of UITextField, is cleared by my app. Since I have many textFields in my app I would like it to be a mechanism from within the subclass.

I found posts that suggest to use observer, and I tried it and it works but I would like a better way.

The problem with this method is that when I enter a single character using the keyboard and then I clear the "Text" from my app using

someField.text = ""

the observer calls my app 50 times, which is very inefficient.

Here is the code I use in myTextField class:

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

and the function that gets the message is

override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {
    if let newValue = change?[NSKeyValueChangeNewKey] {
        print("text changed: \(newValue)")
    }
}

The print() is called more than 50 times with "newValue" being empty ech time. Also, other textFields that has no data in their "text" property get called 5 times when I set their "text" property to "" from within my app, which is also inefficient.

Answer 1

Ignore my post. I found my problem. I put the "addObserver()" inside "editingRectForBounds()" thinking it is called only once upon initialisation, but found out that is called many times, so I had more than 50 "observers". Once I fixed it the app works as expected.