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;
  }
}

score 82 · Accepted Answer · edited Feb 15 '18 at 07:58

82

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.

edited Feb 15 '18 at 07:58

Pang

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answered Feb 19 '09 at 15:11

Stephen Darlington

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23

Right on! A simple [[NSScanner scannerWithString:value] scanInt:nil] will check if "value" has an integer value. Thanks! – Carlos Barbosa Feb 19 '09 at 18:38
What value will integerValue return if the string is empty? – A Salcedo Jul 03 '12 at 14:18
@ASalcedo Presumably you can't rely on the contents if the method returns NO. – Stephen Darlington Jul 03 '12 at 14:54
6

Note `-[NSScanner scanInt:]` returns true for @"00ab" as well -- use `-[NSScanner isAtEnd]` from Steven Green's answer below, or convert into NSNumber (http://stackoverflow.com/questions/1448804/how-to-convert-an-nsstring-into-an-nsnumber?rq=1) to handle such cases – Vivek Jul 13 '13 at 01:12

score 45 · Answer 2 · answered Feb 21 '09 at 05:15

45

Something like this:

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

answered Feb 21 '09 at 05:15

Steven Green

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score 8 · Answer 3 · edited May 23 '17 at 11:46

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"
}

score 2 · Answer 4 · answered May 19 '16 at 17:47

2

Do not forget numbers with decimal point!!!

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

answered May 19 '16 at 17:47

TtheTank

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score 0 · Answer 5 · answered Apr 01 '19 at 08:23

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

NSString is integer?

5 Answers5

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