Backbone.js collection options

javascript backbone.js backbone.js-collections
Jens picture Jens · Dec 11, 2011 · Viewed 37.3k times · Source

I have written a model/view/collection using Backbone.js. My collection uses the fetch method to load the models from a remote server. The url required for this collection needs an id like: messages/{id}. But I have found no clean way to pass options to the Collection.

The backbone.js view accepts options by passing it on construction: view([options]), but the collection expects a list of models upon construction: collection([models]).

What is the "cleanest" way of passing parameters/options to this collection?

Shortened code:

var Messages = Backbone.Collection.extend({
 model: Message,
   url: 'http://url/messages/' + id
});

Answer

nrabinowitz picture nrabinowitz · Dec 11, 2011

@Paul's answer is good, but it's also worth noting that the url attribute can be a function. In my opinion (and it's just opinion, since the end result is the same), the code is a little more legible, if more verbose, if you set the id in initialize and the reference it in a function:

var Messages = Backbone.Collection.extend({
  initialize: function(models, options) {
    this.id = options.id;
  },
  url: function() {
    return '/messages/' + this.id;
  },
  model: Message,
});

var collection = new Messages([], { id: 2 });
collection.fetch();

Just to make sure, though - you aren't confusing the id here with the Model id, are you? @Paul's answer, and my code above, assume that you have multiple Messages collections, each with its own id. If the API path /messages/<id> actually refers to a message, not a set of messages, then you only need to set the url to /messages/ in the Collection, and Backbone will automatically use /messages/<id> for each model.

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