title: Checking if this is null
body: <p>Does it ever make sense to check if <em>this</em> is null?</p>
  
  <p>Say I have a class with a method; inside that method, I check <code>this == NULL</code>, and if it is, return an error code.</p>
  
  <p>If <em>this</em> is null, then that means the object is deleted. Is the method even able to return anything?</p>
  
  <p><strong>Update:</strong> I forgot to mention that the method can be called from multiple threads and it may cause the object to be deleted while another thread is inside the method.</p>