How to identify whether a number is a UPC code or just simple number ? is there any particular format to identify a UPC code?

Question

Is there any format we can use to identify UPC code instead of checking only for number of digits ?

Answer 1

I have some Objective-C code that validates a user entered string to see if it is a valid UPC or EAN barcode. This supports UPC, ISBN, and EAN (8, 13, and 14).

If you have a number, convert it to a string first to use this method. This method assumes that the barcode string only has digits 0-9 or an X (some ISBN barcodes can have an X).

- (BOOL)validBarcode:(NSString *)code {
    int len = [code length];
    switch (len) {
        case 8: // EAN-8
        {
            int check = [code intForDigitAt:7];
            int val = (10 - 
                       (([code intForDigitAt:1] + [code intForDigitAt:3] + [code intForDigitAt:5] +
                         ([code intForDigitAt:0] + [code intForDigitAt:2] + [code intForDigitAt:4] + [code intForDigitAt:6]) *
                         3) % 10)) % 10;

            return check == val;
        }
        case 10: // ISBN
        {
            int check = [code intForDigitAt:9];
            int sum = 0;
            for (int i = 0; i < 9; i++) {
                sum += [code intForDigitAt:i] * (i + 1);
            }
            int val = sum % 11;

            if (val == 10) {
                return [code characterAtIndex:9] == 'X' || [code characterAtIndex:9] == 'x';
            } else {
                return check == val;
            }
        }
        case 12: // UPC
        {
            int check = [code intForDigitAt:11];
            int val = (10 - 
                       (([code intForDigitAt:1] + [code intForDigitAt:3] + [code intForDigitAt:5] + [code intForDigitAt:7] + [code intForDigitAt:9] + 
                         ([code intForDigitAt:0] + [code intForDigitAt:2] + [code intForDigitAt:4] + [code intForDigitAt:6] + [code intForDigitAt:8] + [code intForDigitAt:10]) *
                         3) % 10)) % 10;

            return check == val;
        }
        case 13: // EAN-13
        {
            int check = [code intForDigitAt:12];
            int val = (10 - 
                       (([code intForDigitAt:0] + [code intForDigitAt:2] + [code intForDigitAt:4] + [code intForDigitAt:6] + [code intForDigitAt:8] + [code intForDigitAt:10] + 
                         ([code intForDigitAt:1] + [code intForDigitAt:3] + [code intForDigitAt:5] + [code intForDigitAt:7] + [code intForDigitAt:9] + [code intForDigitAt:11]) *
                         3) % 10)) % 10;

            return check == val;
        }
        case 14: // EAN-14
        {
            int check = [code intForDigitAt:13];
            int val = (10 - 
                       (([code intForDigitAt:1] + [code intForDigitAt:3] + [code intForDigitAt:5] + [code intForDigitAt:7] + [code intForDigitAt:9] + [code intForDigitAt:11] + 
                         ([code intForDigitAt:0] + [code intForDigitAt:2] + [code intForDigitAt:4] + [code intForDigitAt:6] + [code intForDigitAt:8] + [code intForDigitAt:10] + [code intForDigitAt:12]) *
                         3) % 10)) % 10;

            return check == val;
        }
        default:
            return NO;
    }
}

This makes use of a category method I added to NSString:

- (int)intForDigitAt:(NSUInteger)index {
    unichar ch = [self characterAtIndex:index];
    if (ch >= '0' && ch <= '9') {
        return ch - '0';
    } else
        return 0;
}