title: ! vs == nil in objective-c
body: <p>If you have an object like NSString *someString, what is the difference, if any, between</p>
  
  <pre><code>if (!someString)
  </code></pre>
  
  <p>vs</p>
  
  <pre><code>if (someString == nil)
  </code></pre>
  
  <p>Thanks!</p>