Detecting a change to text in UITextfield

Question

I would like to be able to detect if some text is changed in a UITextField so that I can then enable a UIButton to save the changes.

Answer 1

Take advantage of the UITextFieldTextDidChange notification or set a delegate on the text field and watch for textField:shouldChangeCharactersInRange:replacementString.

If you want to watch for changes with a notification, you'll need something like this in your code to register for the notification:

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textFieldDidChange:) name:UITextFieldTextDidChangeNotification object:theTextField];

Here theTextField is the instance of UITextField that you want to watch. The class of which self is an instance in the code above must then implement textFieldDidChange, like so:

- (void)textFieldDidChange:(NSNotification *)notification {
    // Do whatever you like to respond to text changes here.
}

If the text field is going to outlive the observer, then you must deregister for notifications in the observer's dealloc method. Actually it's a good idea to do this even if the text field does not outlive the observer.

- (void)dealloc {
    [[NSNotificationCenter defaultCenter] removeObserver:self];
    // Other dealloc work
}