title: Keeping models consistent across 2 collections when setting attributes and cloning in Backbone?
body: <p>I need to keep the models used in 2 collections <code>Movies</code> and <code>Watchlist</code> the same at all times, both collections use the same model but I need to clone models and add them to <code>Watchlist</code> as well as set attributes <code>watchlist: true/false</code> depending if added or removed. My problem is that when I clone and log out my 2 collections the models <code>watchlist</code> attributes don't match up. Can anyone advise how to resolve this?</p>
  
  <p>A snippet of my add and remove methods</p>
  
  <pre><code>onWatchlistAdd: function(model) {
      console.log('AppView::onWatchlistAdd', model);
  
      model.set('watchlist', true);
  
      var clonedFilm = model.clone();
  
      dataStore.watchlist.add(clonedFilm);
  
      clonedFilm.save();
  
      console.info(dataStore.watchlist);
  },
  
  onWatchlistRemove: function(model) {
      console.log('AppView::onWatchlistRemove', model);
  
      model.set('watchlist', false);
  
      console.log(dataStore.watchlist.toJSON()); //model 1 = watchlist:true
      console.log(dataStore.movies.toJSON()); // model 1 = watchlist:false
  
      dataStore.watchlist.remove(model);
  
      model.destroy();
  }
  </code></pre>