title: In this string number method do I have to alloc every time it is called?
body: <p>Using other answers in this forum I made this class method to tell if a string is a number. It works OK but do I have to alloc-init every time it is called? 
  After all if this was not XCode4 that would constitute a memory leak wouldn't it?
  NB, I am using XCode4 which has the Automatic Reference Counter which will prevent that happening.</p>
  
  <p>I was hoping to do something like</p>
  
  <pre><code>if this is not alloc-initted then alloc-init 
  </code></pre>
  
  <p>but can't seem to get it to work.</p>
  
  <p>Method as it stands currently</p>
  
  <pre><code>+ (BOOL)isThisANumber:(NSString *)candidate{
  
  NSNumberFormatter *fmtr = [[NSNumberFormatter alloc] init];
  [fmtr setNumberStyle:NSNumberFormatterDecimalStyle];
  NSNumber *myNumber = [fmtr numberFromString:candidate];
  if ( myNumber== nil) {
      return NO;
      } 
  else{
      return YES;
      }
  </code></pre>