How to check if contents of a string are numeric values?

Question

I have seen this question but it is 2 years old. Is there a better\easier\newer way to check if string has numeric values. e.g 1 or 1.54 or -1 or -1.54 etc etc.

possible duplicate of [How to convert an NSString into an NSNumber](http://stackoverflow.com/questions/1448804/how-to-convert-an-nsstring-into-an-nsnumber) — Dave DeLong, Oct 06 '11 at 02:35
Thanks @Dave, I added that method and attribution to my answer. — zaph, Oct 06 '11 at 03:00

score 7 · Accepted Answer · edited May 23 '17 at 12:15

7

bool status;
NSScanner *scanner;
NSString *testString;
double result;

scanner = [NSScanner scannerWithString:testString];
status = [scanner scanDouble:&result];
status = status && scanner.scanLocation == string.length;

If status == YES then the string is fully numeric.

Or as @Dave points out from this SO answer:

NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
[formatter setNumberStyle:NSNumberFormatterDecimalStyle];
number = [formatter numberFromString:string];
status = number != nil;

(I'm not leaking, I'm using ARC :-))

edited May 23 '17 at 12:15

Community

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answered Oct 06 '11 at 02:39

zaph

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For a the few weeks that I have spent in Objective C I will take any thing to avoid alloc\init.BTW `(I'm not leaking, I'm using ARC :-))`please elaborate might be handy tip for a beginner like myself. – Java Ka Baby Oct 06 '11 at 03:28
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Well, if `alloc/init` bother you so much you can use `new` albeit it is deprecated: NSNumberFormatter *formatter = `[NSNumberFormatter new];` but I don't suggest that. ARC (Automatic Referencing Counting), available in Xcode 4.2 and IOS 4.3 and above eliminates the need for `retain`, `release' or `autorelease`, in fact they are not allowed. OK, my comment: it is common to get a comment that a release is missing from a code snippet, my snarky comment was directed to that possibility, eventually we will need to come to grips with release/autorelease not being necessary in code under ARC. – zaph Oct 06 '11 at 03:36

score -1 · Answer 2 · answered Oct 06 '11 at 02:13

-1

you can use [NSString floatValue]

answered Oct 06 '11 at 02:13

Foo Bah

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Thant won't work, it will return 0 for garbage, the same as for @"0". – zaph Oct 06 '11 at 02:19
the question is not how to convert but how to check if the string can be converted to some numeric value – shebelaw Jan 27 '13 at 19:32

How to check if contents of a string are numeric values?

2 Answers2

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