javascript - Why doesn't Backbone Collection fetch return a promise - Stack Overflow

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The following example code works well:

Auth_controller.prototype.isLogged = function(){ 
    //Check if the user is authenticated 
    var getAuthStatus = this.auth_model.fetch(); 
    return getAuthStatus; 
}; 

Auth_controller.prototype.redirect = function(fragment, args, next){ 

    var getAuthStatus = this.isLogged(); 
    var self = this; 

    $.when(getAuthStatus).then(function(response){ 
        //Do something with the response 
    }
}); 

This doesn't seem to work for a Collection though.
When I console log the collection, I get an empty collection back.

I know that I can use the success callback function from within the method (tested that already), but I don't want to do that, because I want the function to return a promise that I can call from other functions as well.
Edit -> No, sorry it doesn't work in the success callback either so it seems.

Any suggestions for a workaround ?

Edit;

This image shows what is returned from the model and collection fetch methods.
Unless I'm doing something wrong that is obvious, I don't understand why this happens.
When console logging the returned response in the success callback, I see that the empty object as shown in the screenshot, gets populated.

Edit2:

This is what my collection looks like:

define([
  /*--- libraries ---*/
  'jquery',     
  'underscore', 
  'backbone', 

  /*--- model ---*/
  'models/users/role_model'

], function($, _, Backbone, 
                Role_model){

    var Role_collection = Backbone.Collection.extend({ 
        url: '/ingeb/api_v1/users/roles', 
        model: Role_model 
    }); 

    return Role_collection; 

}); 

The following example code works well:

Auth_controller.prototype.isLogged = function(){ 
    //Check if the user is authenticated 
    var getAuthStatus = this.auth_model.fetch(); 
    return getAuthStatus; 
}; 

Auth_controller.prototype.redirect = function(fragment, args, next){ 

    var getAuthStatus = this.isLogged(); 
    var self = this; 

    $.when(getAuthStatus).then(function(response){ 
        //Do something with the response 
    }
}); 

This doesn't seem to work for a Collection though.
When I console log the collection, I get an empty collection back.

I know that I can use the success callback function from within the method (tested that already), but I don't want to do that, because I want the function to return a promise that I can call from other functions as well.
Edit -> No, sorry it doesn't work in the success callback either so it seems.

Any suggestions for a workaround ?

Edit;

This image shows what is returned from the model and collection fetch methods.
Unless I'm doing something wrong that is obvious, I don't understand why this happens.
When console logging the returned response in the success callback, I see that the empty object as shown in the screenshot, gets populated.

Edit2:

This is what my collection looks like:

define([
  /*--- libraries ---*/
  'jquery',     
  'underscore', 
  'backbone', 

  /*--- model ---*/
  'models/users/role_model'

], function($, _, Backbone, 
                Role_model){

    var Role_collection = Backbone.Collection.extend({ 
        url: '/ingeb/api_v1/users/roles', 
        model: Role_model 
    }); 

    return Role_collection; 

}); 

• javascript
• jquery
• backbone.js
• promise
• backbone.js-collections

Share Improve this question Follow edited Apr 9, 2014 at 16:16 Trace asked Apr 9, 2014 at 15:27 TraceTrace 18.9k2121 gold badges9696 silver badges171171 bronze badges 3

• Where exactly do you get an empty collection, and in what callback do you see that it should contain some items actually? – Bergi Commented Apr 9, 2014 at 15:34
• I have added a screenshot. In the jQuery when - then callback. It works well for the model, but when using the same method for the collection, it doesn't work... – Trace Commented Apr 9, 2014 at 15:44
• 1 This is what Collection.prototype.fetch returns: return this.sync('read', this, options); github./jashkenas/backbone/blob/master/backbone.js#L885-L898 in turn, sync does return Backbone.sync.apply(this, arguments); in turn which returns a promise. Is it possible you've overwritten .sync for this particular collection? Can you show us the code for that collection? – Benjamin Gruenbaum Commented Apr 9, 2014 at 15:56

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1 Answer 1

Sorted by: Reset to default 10

Actually, the collection's fetch does return a promise:

Delegates to Backbone.sync under the covers for custom persistence strategies and returns a jqXHR.

See http://backbonejs/#Collection-fetch and http://api.jquery./jQuery.ajax/#jqXHR

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