title: How to check if NSString is contains a numeric value?
body: <p>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 different for instance display an error message.</p>
  
  <p>I have been having a look round but am finding it hard to find anything that works along the lines of what I am wanting to do. I have looked at NSScanner but I am not sure if its checking the whole string and then I am not actually sure how to check if these characters are numeric</p>
  
  <pre><code>- (void)isNumeric:(NSString *)code{
  
      NSScanner *ns = [NSScanner scannerWithString:code];
      if ( [ns scanFloat:NULL] ) //what can I use instead of NULL?
      {
          NSLog(@"INSIDE IF");
      }
      else {
      NSLog(@"OUTSIDE IF");
      }
  }
  </code></pre>
  
  <p>So after a few more hours searching I have stumbled across an implementation that dose exactly what I am looking for.</p>
  
  <p>so if you are looking to check if their are any alphanumeric characters in your NSString this works here</p>
  
  <pre><code>-(bool) isNumeric:(NSString*) hexText
  {
  
      NSNumberFormatter* numberFormatter = [[[NSNumberFormatter alloc] init] autorelease];
  
      NSNumber* number = [numberFormatter numberFromString:hexText];
  
      if (number != nil) {
          NSLog(@"%@ is numeric", hexText);
          //do some stuff here      
          return true;
      }
  
      NSLog(@"%@ is not numeric", hexText);
      //or do some more stuff here
      return false;
  }
  </code></pre>
  
  <p>hope this helps. </p>