title: How to create a utility class that has common helpers?
body: <p>I want to create a utility class with common functions I need.  So they have to be static, and not leak memory.</p>
  
  <p>Say I wanted to add this function that converts a NSString to a NSNumber:</p>
  
  <pre><code>NSNumberFormatter * f = [[NSNumberFormatter alloc] init];
  [f setNumberStyle:NSNumberFormatterDecimalStyle];
  NSNumber * myNumber = [f numberFromString:@"42"];
  [f release];
  </code></pre>
  
  <p>How could I return the result, and not leak?</p>
  
  <p>Would i have to use autorelease for this?</p>