Swift 2.0和Xcode-beta 7.0 –使用UITextField进行数字输入

Question

Completely frustrated noob here. Surely this isn't as hard as it looks?

I want to use a number entered by the user, perform a calculation, and send the result back to the screen.

I have code working that can use a string forced in by code, convert it to double, do the math and send the result to the screen. For example:

 @IBAction func buttonPressed() {
  NSLog("Button Pressed")

  let decimalAsString = "123.45"
  let decimalAsDouble = NSNumberFormatter().numberFromString(decimalAsString as String)!.doubleValue
   TempLabel.text = "\(decimalAsDouble+2.45)"
}

This simply adds 2.45 to the string "123.45" and sends the result 125.9 back as a string to my label for display, all when the button is pressed. Great. This simpler form also works:

        let decimalAsDouble = Double(decimalAsString)

What I have been struggling with is using a number entered into the UITextField.

My UITextField uses a decimal pad for entry, and I've always had a number entered there when the errors were thrown. (Or did I? The numbers show on screen but are they really "entered"? Hmmm...)

No matter what I try, I cannot find code that will both compile and then not blow up at execution, when the button is pressed. The error I get generally complains about unwrapping an optional nil.

I can detail some of the things that DON'T work, if that helps.

Answer 1

OK, well I've finally solved my own problem. My problem was with closing the entry field and dismissing the numeric entry pad. Once I did that, the entered value became available.

The critical code, in the view controller, was:

func textFieldShouldReturn(textField: UITextField!) -> Bool {   //delegate method
    textField.resignFirstResponder()
    return true
}

override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?){
    view.endEditing(true)
    super.touchesBegan(touches, withEvent: event)
}

This dismisses the entry pad when the user clicks anywhere in the view except for the field itself or a button. Programming that looks for the entered value doesn't blow up.