Singapore NRIC Validation

sg-nric-validation.m

- (BOOL)validateNRIC:(NSString*)nric {
    nric = [nric uppercaseString];
    
    // NRIC length should be 9
    if ([nric length]!=9) {
        return NO;
    }
    
    //NRIC.charAt( 0 ) should be “S” or “T”
    unichar prefix = [nric characterAtIndex:0];
    if ((prefix != 'S') && (prefix != 'T')) {
        return NO;
    }
    
    //int number = NRIC.substring( 1, 8 )
    //If “number” is not numeric then False
    
    NSString *number = [nric substringWithRange:NSMakeRange(1, 7)];
    NSMutableCharacterSet *numbers = [NSCharacterSet decimalDigitCharacterSet];
    if ([number rangeOfCharacterFromSet:[numbers invertedSet]].location != NSNotFound) {
        return NO;
    }
    
    NSInteger sum = 0;
    
    sum += ([number characterAtIndex:0]-48) * 2;
    sum += ([number characterAtIndex:1]-48) * 7;
    sum += ([number characterAtIndex:2]-48) * 6;
    sum += ([number characterAtIndex:3]-48) * 5;
    sum += ([number characterAtIndex:4]-48) * 4;
    sum += ([number characterAtIndex:5]-48) * 3;
    sum += ([number characterAtIndex:6]-48) * 2;
    
    if (prefix=='T') {
        sum += 4;
    }
    
    NSInteger p = 11-sum%11;
    unichar suffix = [nric characterAtIndex:8];
    
    switch (p) {
        case 1:
            if (suffix == 'A')
                return YES;
            break;
        case 2:
            if (suffix == 'B')
                return YES;
            break;
        case 3:
            if (suffix == 'C')
                return YES;
            break;
        case 4:
            if (suffix == 'D')
                return YES;
            break;
        case 5:
            if (suffix == 'E')
                return YES;
            break;
        case 6:
            if (suffix == 'F')
                return YES;
            break;
        case 7:
            if (suffix == 'G')
                return YES;
            break;
        case 8:
            if (suffix == 'H')
                return YES;
            break;
        case 9:
            if (suffix == 'I')
                return YES;
            break;
        case 10:
            if (suffix == 'Z')
                return YES;
            break;
        case 11:
            if (suffix == 'J')
                return YES;
            break;
            
        default:
            break;
    }
    return NO;
}