title: Whats the difference between @observable and @observable.ref modifiers in mobx?
body: <p>Mobx supports both @observable and @observable.ref modifiers and their official doc says </p>
  
  <pre><code>observable: This is the default modifier, used by any observable. It clones and converts any (not yet observable) array, Map or plain object into it's observable counterpart upon assignment to the given property
  
  observable.ref: Disables automatic observable conversion, just creates an observable reference instead.
  </code></pre>
  
  <p>I do not understand why would we need to create a observable reference for an already existing observable. How are these two different and what are their use cases ?</p>