Question

I am fetching a mongodb collection from server using backbone collection. Since the ids are stored as ‘_id’, I used idAttribute to map it to ‘_id’.

(function(){
  var PlaceModel = Backbone.Model.extend({
    idAttribute: "_id",
  });
  var PlaceCollection = Backbone.Collection.extend({
    url: "http://localhost:9090/places",
    initialize: function(options){
      var that = this;
      this.fetch({
        success: function(){
          console.log("Success!", that.toJSON());
        },
        error: function(){
          console.log("Error");
        }
      });
    }
  });

  var place = new PlaceCollection({model:PlaceModel});

}()); 

But later on when I try to access the model’s ‘idAttribute’ when it’s time to DELETE an entry, it returns ‘id’ instead of ‘_id’, which means this.model.isNew() from the view returns ‘true’ for all the records fetched from the server. Therefore I cannot DELETE nor PUT an entry to the server.

However if I set the idAttribute using prototype like this (instead of inside the PlaceModel definition):

Backbone.Model.prototype.idAttribute = "_id";

Then it correctly maps the idAttribute to ‘_id’, and everything works. What might be happening?

Answer 1

When you say this:

var place = new PlaceCollection({model:PlaceModel});

That’s the same, more or less, as saying this:

var o     = new Backbone.Model({ model: PlaceModel });
var place = new PlaceCollection([ o ]);

You’re not setting the collection “class”‘s model property, you’re just creating a collection with one model in it (a plain Backbone.Model instance, not a PlaceModel) and that model has a model attribute with value PlaceModel.

So, given all that, the collection has no idea that its model is supposed to have idAttribute: "_id" or even that its model is supposed to be a PlaceModel. You want to see the model when you create PlaceCollection, not when you create place:

var PlaceCollection = Backbone.Collection.extend({
  url: "http://localhost:9090/places",
  model: PlaceModel,
  //...
});

var place = new PlaceCollection;