title: What is the best way to store the state of NSTreeController contents in Swift?
body: <p>I've built the custom <code>NSOutlineView</code> with <code>NSTreeController</code>, and I faced with the huge complexity of saving its state. Usage of <code>Core Data</code> is too tedious since I have implemented drag and drop support as well.</p>
  
  <p>So my question is more general. What is the best way to save <code>NSTreeController</code>'s state? Is it achievable with <code>NSCoding</code>?</p>
  
  <p>Thanks in advance.</p>