UITextField: Password Implementation

Question

I have a OTP Screen, where I have to enter the OTP in 4 digit password in 4 Diff TextFields, The scenario is like this :

1. A max character limit for each textfield is 1 and when the user enters a character in textfield it should move to next TextField.
2. When the user clicks on back space, it should take back to previous textfield inorder to make the changes.

I have managed the working up to 70% but back space works only when the user enters all the textField. I'm pasting out my code.

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    // This allows numeric text only, but also backspace for deletes
    if (string.length > 0 && ![[NSScanner scannerWithString:string] scanInt:NULL])
        return NO;

    NSUInteger oldLength = [textField.text length];
    NSUInteger replacementLength = [string length];
    NSUInteger rangeLength = range.length;

    NSUInteger newLength = oldLength - rangeLength + replacementLength;

    // This 'tabs' to next field when entering digits
    if (newLength == 1) {
        if (textField == _pin1)
        {
            [self performSelector:@selector(setNextResponder:) withObject:_pin2 afterDelay:0];
        }
        else if (textField ==_pin2)
        {
            [self performSelector:@selector(setNextResponder:) withObject:_pin3 afterDelay:0];
        }
        else if (textField == _pin3)
        {
            [self performSelector:@selector(setNextResponder:) withObject:_pin4 afterDelay:0];
        }
    }
    //this goes to previous field as you backspace through them, so you don't have to tap into them individually
    else if (oldLength > 0 && newLength == 0) {
        if (textField ==_pin4)
        {
            [self performSelector:@selector(setNextResponder:) withObject:_pin3 afterDelay:0];
        }
        else if (textField == _pin3)
        {
            [self performSelector:@selector(setNextResponder:) withObject:_pin2 afterDelay:0];
        }
        else if (textField == _pin2)
        {
            [self performSelector:@selector(setNextResponder:) withObject:_pin1 afterDelay:0];
        }
    }        
    return newLength <= 1;
}

- (void)setNextResponder:(UITextField *)nextResponder
{
    [nextResponder becomeFirstResponder];
}

working:

Answer 1

Need to give tag into UITextView in StoryBoard.

Like textField1 = 101,textField2 = 102,textField3 = 103,textField4 = 104

Put following code into your viewcontroller.

- (BOOL)keyboardInputShouldDelete:(UITextField *)textField {
    BOOL shouldDelete = YES;

    if ([textField.text length] == 0 && [textField.text isEqualToString:@""]) {
        long tagValue = textField.tag - 1;
        UITextField *txtField = (UITextField*) [self.view viewWithTag:tagValue];

        [txtField becomeFirstResponder];
    }
    return shouldDelete;
}

Following code for the next UItextField Focus.

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    // This allows numeric text only, but also backspace for deletes
    if (string.length > 0 && ![[NSScanner scannerWithString:string] scanInt:NULL])
        return NO;

    if ([textField.text length] == 0) {
        [self performSelector:@selector(changeTextFieldFocusToNextTextField:) withObject:textField afterDelay:0.3];
    }

    return YES;
}

-(void)changeTextFieldFocusToNextTextField:(UITextField*)textField{
    long tagValue = textField.tag + 1;
    UITextField *txtField = (UITextField*) [self.view viewWithTag:tagValue];
    [txtField becomeFirstResponder];
}

Sample Output

Grab the solution demo project