UITextField allowing only 1 decimal and no decimals at the beginning

gistfile1.m

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    NSCharacterSet *nonNumberSet = [[NSCharacterSet characterSetWithCharactersInString:@"0123456789."] invertedSet];
    // allow backspace
    if (range.length > 0 && [string length] == 0)
    {
        return YES;
    }
// Comment out to allow decimal at the beginning
    // do not allow . at the beggining
    if (range.location == 0 && [string isEqualToString:@"."])
    {
        return NO;
    }
    
    // User already has 1 decimal -don't allow a second one.
    if ( [textField.text rangeOfString: @"."].location == NSNotFound )
    {
        return YES;
    }
    else
    {
        // If entering __ANOTHER__DECIMAL__ don't allow it
        if (  [string isEqualToString: @"."] )
        {
            return NO;
        }
        else // If its anything but another decimal -- allow it.
        {
            // set the text field value manually
            NSString *newValue = [[textField text] stringByReplacingCharactersInRange:range withString:string];
            newValue = [[newValue componentsSeparatedByCharactersInSet:nonNumberSet] componentsJoinedByString:@""];
            textField.text = newValue;
            // return NO because we're manually setting the value
            return NO;
        }
    }
}