Moving the cursor once max length is reached - objective-c

Question

I've crudely put together this code based on some other answers on SO but I still can't get it to work. I want my cursor to move to the next textField once a certain length has been reached, and it does that...to an extent.
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
if (textField.tag == 0 && range.location >= 1) {
[_secondTextField becomeFirstResponder];
return YES;
} else if (textField.tag == 1 && range.location >= 2) {
[_thirdTextField becomeFirstResponder];
return YES;
} else if (textField.tag == 2 && range.location >= 1) {
[_fourthTextField becomeFirstResponder];
return YES;
} else {
return YES;
}
}
...
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
// catched the delegates for the input textfields
_firstTextField.delegate = self;
_secondTextField.delegate = self;
_thirdTextField.delegate = self;
[_firstTextField becomeFirstResponder];
}
So I have 4 textfields, and I have character limits of 1, 2, and 1 for the first 3 text fields. The problem right now is the cursor will not move to the next textfield until after I type more text. This next text is in the new textfield, so the overall effect is achieved, but the cursor just isn't moving at the right time.
What can I do so that the cursor will move as soon as I reach the character limit?

Answer 1

A better way would be to use the didChange method like the UITextViewDelegate method, but as we know the UITextFieldDelegate does not have a didChange method. You can manually add behaviour. You can use the shouldChangeCharactersInRange: method, but personally I would advise not to override methods unless you absolutely have to.
You can add behaviour using:
[yourTextField addTarget:self action:#selector(textFieldDidChange:) forControlEvents:UIControlEventEditingChanged];
And in the target method:
- (void)textFieldDidChange:(UITextField*)textField{
if (textField.tag == 0 && textField.text.length == 1){
[_secondTextField becomeFirstResponder];
}else if (textField.tag == 1 && textField.text.length == 2){
[_thirdTextField becomeFirstResponder];
}else if (textField.tag == 2 && textField.text.length == 1){
[_fourthTextField becomeFirstResponder];
}
}