NSString is integer?

Question

How to check if the content of a NSString is an integer value? Is there any readily available way?

There got to be some better way then doing something like this:

- (BOOL)isInteger:(NSString *)toCheck {
  if([toCheck intValue] != 0) {
    return true;
  } else if([toCheck isEqualToString:@"0"]) {
    return true;
  } else {
    return false;
  }
}

Answer 1

You could use the -intValue or -integerValue methods. Returns zero if the string doesn't start with an integer, which is a bit of a shame as zero is a valid value for an integer.

A better option might be to use [NSScanner scanInt:] which returns a BOOL indicating whether or not it found a suitable value.

Answer 2

Something like this:

NSScanner* scan = [NSScanner scannerWithString:toCheck]; 
int val; 
return [scan scanInt:&val] && [scan isAtEnd];

Answer 3

Building on an answer from @kevbo, this will check for integers >= 0:

if (fooString.length <= 0 || [fooString rangeOfCharacterFromSet:[[NSCharacterSet decimalDigitCharacterSet] invertedSet]].location != NSNotFound) {
    NSLog(@"This is not a positive integer");
}

A swift version of the above:

func getPositive(incoming: String) -> String {
    if (incoming.characters.count <= 0) || (incoming.rangeOfCharacterFromSet(NSCharacterSet.decimalDigitCharacterSet().invertedSet) != nil) {
        return "This is NOT a positive integer"
    }
    return "YES! +ve integer"
}

Answer 4

Do not forget numbers with decimal point!!!

NSMutableCharacterSet *carSet = [NSMutableCharacterSet characterSetWithCharactersInString:@"0123456789."];
BOOL isNumber = [[subBoldText stringByTrimmingCharactersInSet:carSet] isEqualToString:@""];

Answer 5

func getPositive(input: String) -> String {
    if (input.count <= 0) || (input.rangeOfCharacter(from: NSCharacterSet.decimalDigits.inverted) != nil) {
        return "This is NOT a positive integer"
    }
    return "YES! integer"
}

Update @coco's answer for Swift 5