iOS - how do I check if a string is numeric or not?

Question

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iPhone how to check that a string is numeric only

I am trying to look up some basic functionality in Objective C, but can't seem to locate the basic answer.

What I really need is to check

if ( some_string is numeric )
{

}

I would assume there would just be some built in function for that. No?

I am looking at this StackOverflow question How to check if NSString is numeric or not and they seem to be doing things the very complicated way.

Isn't there some basic check I can do in one simple line?

Thanks!

Define "numeric"! Are only digits allowed? Minus? Decimal dot? Scientific notation? Different locales? What else... — Nikolai Ruhe, Jul 21 '12 at 00:46

Nikolai Ruhe · Accepted Answer · 2012-07-21T01:04:33.307

38

Isn't there some basic check I can do in one simple line?

No.

NSScanner *scanner = [NSScanner scannerWithString:testString];
BOOL isNumeric = [scanner scanInteger:NULL] && [scanner isAtEnd];

If you want to allow decimal digits exchange scanInteger: by scanDouble:.

edited Jul 21 '12 at 01:04

answered Jul 21 '12 at 00:53

Nikolai Ruhe

Is there any performance penalty on this like with a NSDateFormatter? – agarcian Oct 17 '13 at 23:33
@agarcian No, NSScanner is quite lightweight. – Nikolai Ruhe Mar 17 '14 at 08:01
Does this allow negative numbers too? i.e.: -23.2351 – Supertecnoboff May 11 '16 at 22:22

1 Answers1