How to Test Character Input to UITextField as the User Enters Characters and Prevent Invalid Characters

Question

First, I setup up the keyboard for the UITextField to use the number with decimal style. So the user can only enter numbers and a single decimal.

What I want to do i

Answer 1

You can pass the string of uitexfield to below method, it will return yes/no..accordingly you can show error

- (BOOL) validatePhone: (NSString *) aMobile {
    NSString *phoneRegex = @"^+(?:[0-9] ?){6,14}[0-9]$"; 
    NSPredicate *phoneTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", phoneRegex];
    if (aMobile.length>0) {
        NSString *mobileTextString = [[mobileText.text componentsSeparatedByCharactersInSet:
                                       [[NSCharacterSet decimalDigitCharacterSet] invertedSet]] 
                                      componentsJoinedByString:@""];
        NSString *firstNumber = [aMobile substringToIndex:1];
       if (mobileTextString.length!=10){

            return NO;
        }

    }
        return [phoneTest evaluateWithObject:aMobile];
}