Question

I would like to enable the done button on the navbar (in a modal view) when the user writes at least a char in a uitextfield. I tried:

• textFieldDidEndEditing: enables the button when the previous uitextfield resigns first responder (so with the zero chars in the current uitextfield).
• textFieldShouldBeginEditing: is called when the textfield becomes the first responder.
  Is there another way to do this?

[EDIT]

The solution could be

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string

but neither

 [self.navigationItem.rightBarButtonItem setEnabled:YES];

or

[doneButton setEnabled:YES]; //doneButton is an IBOutlet tied to my Done UIBarButtonItem in IB

work.

Answer 1

The correct code is;

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    NSUInteger length = editingTextField.text.length - range.length + string.length;
    if (length > 0) {
        yourButton.enabled = YES;
    } else { 
        yourButton.enabled = NO;
    }
    return YES;
}

Edit:
As correctly pointed out by MasterBeta before and David Lari later, the event should respond to Editing Changed. I’m updating the answer with David Lari’s solution as this was the one marked as correct.

- (IBAction)editingChanged:(UITextField *)textField
{
   //if text field is empty, disable the button
    _myButton.enabled = textField.text.length > 0;
}