title: Checking a null value in Objective-C that has been returned from a JSON string
body: <p>I have a <strong>JSON</strong> object that is coming from a webserver.</p>
  
  <p>The log is something like this:</p>
  
  <pre><code>{          
     "status":"success",
     "UserID":15,
     "Name":"John",
     "DisplayName":"John",
     "Surname":"Smith",
     "Email":"email",
     "Telephone":null,
     "FullAccount":"true"
  }
  </code></pre>
  
  <p>Note the Telephone is coming in as null if the user doesn't enter one.</p>
  
  <p>When assigning this value to a <code>NSString</code>, in the <code>NSLog</code> it's coming out as <code>&lt;null&gt;</code></p>
  
  <p>I am assigning the string like this:</p>
  
  <pre><code>NSString *tel = [jsonDictionary valueForKey:@"Telephone"];
  </code></pre>
  
  <p>What is the correct way to check this <code>&lt;null&gt;</code> value?  It's preventing me from saving a <code>NSDictionary</code>.</p>
  
  <p>I have tried using the conditions <code>[myString length]</code> and <code>myString == nil</code> and <code>myString == NULL</code></p>
  
  <p>Additionally where is the best place in the iOS documentation to read up on this?</p>