title: objective-c - Get pointer to object's property
body: <p>I have an object <code>Activity</code> which has three <code>NSString</code> properties <code>activityName, activityType, activityDescription</code></p>
  
  <p>I want to do something like this</p>
  
  <pre><code>NSString *currentProperty = activity.activityDescription;
  currentProperty = @"My description";
  </code></pre>
  
  <p>and make <code>activity.activityDescription</code> be automatically updated as I change <code>currentProperty</code></p>
  
  <p>I think it should be possible since I work with pointers, but in practice it doesn't work. What am I doing wrong?</p>