How to implement undo/redo with programatic change of the textValue of a NSTextView?

Question

I created a simple demo app with a NSTextView and a button, the provided a NSTextViewDelegate to the textView and added an action:

- (IBAction)actionButtonClicke         


        

Answer 1

Let's say you want your NSTextView to create a new undo group when user hits the Enter key (Apple Pages behavior). Then you might type this code in your NSTextView subclass:

override func shouldChangeTextInRange(affectedCharRange: NSRange, replacementString: String?) -> Bool {
    super.shouldChangeTextInRange(affectedCharRange, replacementString: replacementString)
    guard replacementString != nil else { return true }

    let newLineSet = NSCharacterSet.newlineCharacterSet()
    if let newLineRange = replacementString!.rangeOfCharacterFromSet(newLineSet) {

        // check whether it's a single character (user hit Return key)
        let singleCharRange = (replacementString!.startIndex)! ..< (replacementString!.startIndex.successor())!
        if newLineRange == singleCharRange {
            self.breakUndoCoalescing()
        }
    }

    return true
}