Textfield.text entered should have a specific format

Question

I have a textfield and I want the text to be entered in it in a format: aa #### 1234 I know this should be done in shouldChangeCharactersInRange delegate method of textfield.nut I am not able to understand that how condition will be implemented on each character.Kindly give your suggestions.Thanks in advance!

Answer 1

Create categories on UITextField and add this method write condition according your requirement. Below example for email id:

 - (BOOL)validateRegEx:(NSString*)regexString
 {
     NSError *error = NULL;
     NSRegularExpression *regex = [NSRegularExpression    regularExpressionWithPattern:regexString
                                                                      options:NSRegularExpressionCaseInsensitive
                                                                         error:&error];
     NSUInteger numberOfMatches = [regex numberOfMatchesInString:self.text
                                                    options:0
                                                      range:NSMakeRange(0, [self.text length])];

    return numberOfMatches > 0;
}

Answer 2

Try this

-(BOOL)checkString:(NSString *)str{
    NSString *regex1 = @"^[a-bA-B0-9]"; // chabge regex as per your needs
    NSPredicate *test1 = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex1];
    return [test1 evaluateWithObject:str] ;
}

Answer 3

An expression that can be helpful to validate your needs might be:

^[a-z]{2}\s\d{4}\s\d{4}$

Here:

• ^ - Shows start of string
• [a-z]{2} - Shows any character between a-z exactly 2 times
• \s - Shows white space character one time.
• \d{4} - Shows any digit from 0-9, exactly 4 times.
• $ - Shows end of string

An example as a workaround could be this, here the tricky part is to allow the under construction string:

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    NSError *error = NULL;
    NSRegularExpression *regex = nil;

     NSMutableString *combinedText = [textField.text mutableCopy];
    [combinedText replaceCharactersInRange:range withString:string];

    switch (combinedText.length) {
        case 1:
        case 2:
            regex = [NSRegularExpression regularExpressionWithPattern:[NSString stringWithFormat:@"^[a-z]{%ld}", (long)combinedText.length] options:NSRegularExpressionCaseInsensitive error:&error];
            break;
        case 3:
            regex = [NSRegularExpression regularExpressionWithPattern:@"^[a-z]{2}\\s" options:NSRegularExpressionCaseInsensitive error:&error];
            break;
        case 4:
        case 5:
        case 6:
        case 7:
            regex = [NSRegularExpression regularExpressionWithPattern:[NSString stringWithFormat:@"^[a-z]{2}\\s\\d{%ld}", (long)combinedText.length - 3] options:NSRegularExpressionCaseInsensitive error:&error];
            break;
        case 8:
            regex = [NSRegularExpression regularExpressionWithPattern:@"^[a-z]{2}\\s\\d{4}\\s" options:NSRegularExpressionCaseInsensitive error:&error];
            break;
        case 9:
        case 10:
        case 11:
        case 12:
            regex = [NSRegularExpression regularExpressionWithPattern:[NSString stringWithFormat:@"^[a-z]{2}\\s\\d{4}\\s\\d{%ld}$", (long)combinedText.length - 8] options:NSRegularExpressionCaseInsensitive error:&error];
            break;
        default:
            return false;
    }

    if(error) return false;        

    NSUInteger numberOfMatches = [regex numberOfMatchesInString:combinedText options:0 range:NSMakeRange(0, combinedText.length)];
    return numberOfMatches > 0 || string.length == 0;
}

Hope that helps!