Question

this.id is undefined in Blog.Collections.Posts class. What’s wrong?

Blog collection

Blog.Collections.Posts = Backbone.Collection.extend({

  model: Blog.Models.Post,
  url: function() {
    console.log(this.id);
    if (this.id) {
      return '/api/posts/'+this.id
    }
    else{
      return '/api/posts'
    }
  }

});

My router:

Blog.Routers.Posts = Backbone.Router.extend({

    routes: {
    ""                  :        "index",
    "entry/:id" :        "show"
  },

  show: function(id) {
    var collection = new Blog.Collections.Posts({id: id});
    collection.fetch({
      success: function() {
        var view = new Blog.Views.PostsIndex({ collection: collection });
        console.log(collection);
      }
    });
  }

});

Answer 1

Collections don’t have an id by default. Unless you’re explicitly assigning an id to your collection, this.id becomes undefined. IDs are standard attribute of models. What you want to do is simply:

// Collection URL
url: function() {
    return '/api/posts'
}

Backbone models, if they are a part of a collection will use the collection url when fetching and saving. Thus, if you do something like this:

// myModel is a part of the collection
myModel.save();

It will automatically goto:

'/api/posts/:id'  // Assuming your model already has a model.id

Hope this helps.