How to check if NSString is contains a numeric value?

Question

I have a string that is being generate from a formula, however I only want to use the string as long as all of its characters are numeric, if not that I want to do something dif

Answer 1

Consider NSString integerValue - it returns an NSInteger. However, it will accept some strings that are not entirely numeric and does not provide a mechanism to determine strings which are not numeric at all. This may or may not be acceptable.

For instance, " 13 " -> 13, "42foo" -> 42 and "helloworld" -> 0.

Happy coding.

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Now, since the above was sort of a tangent to the question, see determine if string is numeric. Code taken from link, with comments added:

BOOL isNumeric(NSString *s)
{
   NSScanner *sc = [NSScanner scannerWithString: s];
   // We can pass NULL because we don't actually need the value to test
   // for if the string is numeric. This is allowable.
   if ( [sc scanFloat:NULL] )
   {
      // Ensure nothing left in scanner so that "42foo" is not accepted.
      // ("42" would be consumed by scanFloat above leaving "foo".)
      return [sc isAtEnd];
   }
   // Couldn't even scan a float :(
   return NO;
}

The above works with just scanFloat -- e.g. no scanInt -- because the range of a float is much larger than that of an integer (even a 64-bit integer).

This function checks for "totally numeric" and will accept "42" and "0.13E2" but reject " 13 ", "42foo" and "helloworld".