Question

When is it appropriate to filter a collection vs. having several collections in Backbone?

For example, consider a music library app. It would have a view for displaying genres and another view for displaying the selected genre’s music.

Would you rather make one huge collection with all the music and then filter it or several smaller ones?

Having just one collection would allow you add features for filtering by other attributes as well, but suppose you have tons of music: how do you prevent loading it all in when the application starts if the user if only going to need 1 genre?

Answer 1

I think the simplest approach is having a common unique Collection that, intelligently, fetch an already filtered by genre data from the server:

// code simplified and no tested
var SongsCollection = Backbone.Collection.extend({
  model: Song,
  url: function() {
    return '/songs/' + this.genre;
  },
  initialize: function( opts ){
    this.genre = opts.genre;
  }
});

var mySongsCollection = new SongsCollection({ genre: "rock" });
mySongsCollection.fetch();

You have to make this Collection to re-fetch data from the server any time the User changes the selected genre:

mySongsCollection.genre = "punk";
mySongsCollection.fetch();