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POEmber-Data: How do "mappings" work
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copied!<p>I'm currently trying to put something together with ember + emberdata + router + asp.net web api. Most of it seem to work, however I stuck in an error message I get when ember-data tries to <code>findAll</code> through the adapter for my models.</p> <p>In my backend I have a model like this (C#):</p> <pre><code>public class Genre { [Key] public int Id { get; set; } [Required] [StringLength(50, MinimumLength=3)] public string Name { get; set; } } </code></pre> <p>Which in my app I represent it like this using ember-data:</p> <pre><code>App.Genre = DS.Model.extend({ id: DS.attr("number"), name: DS.attr("string") }).reopenClass({ url: 'api/genre' }); </code></pre> <p>I have also a Store defined in my App using the RESTAdapter like so:</p> <pre><code>App.store = DS.Store.create({ revision: 4, adapter: DS.RESTAdapter.create({ bulkCommit: false }) }); </code></pre> <p>And the store is used in my controller as below:</p> <pre><code>App.GenreController = Ember.ArrayController.extend({ content: App.store.findAll(App.Genre), selectedGenre: null }); </code></pre> <p>The router is defined as</p> <pre><code>App.router = Em.Router.create({ enableLogging: true, location: 'hash', root: Ember.Route.extend({ //... genre: Em.Route.extend({ route: '/genre', index: Ember.Route.extend({ connectOutlets: function (router, context) { router.get('applicationController').connectOutlet('genre'); } }) }), //... }) }) </code></pre> <p>When I run my application, I get the following message for every object that has this same structure:</p> <blockquote> <p>Uncaught Error: assertion failed: Your server returned a hash with the key 0 but you have no mappings</p> </blockquote> <p>For reference, here's the json the service is returning:</p> <pre><code>[ { "id": 1, "name": "Action" }, { "id": 2, "name": "Drama" }, { "id": 3, "name": "Comedy" }, { "id": 4, "name": "Romance" } ] </code></pre> <p>I cannot tell exactly what the problem is and since the assertion is mentioning that I need mapping, I'd like to know:</p> <ol> <li>What this mapping <em>is</em> and how to use it. </li> <li>Since the returned json is an array, should I be using a different type of controller in my app ,or is there anything I should know about when working with this type of json in ember-data? or should I change the JsonFormatter options in the server? </li> </ol> <p>Any help is welcome.</p> <p>I can definitely add more information if you feel this isn't enough to understand the problem.</p> <p><strong>EDIT</strong>: I've changed a few things in my backend and now my <code>findAll()</code> equivalent action in the server serializes the the output as the following json:</p> <pre><code>{ "genres": [ { "id": 1, "name": "Action" }, { "id": 2, "name": "Drama" }, { "id": 3, "name": "Comedy" }, { "id": 4, "name": "Romance" } ] } </code></pre> <p>But I still can't get it to populate my models in the client and my error message has changed to this:</p> <blockquote> <p>Uncaught Error: assertion failed: Your server returned a hash with the key genres but you have no mappings</p> </blockquote> <p>Not sure what else I might be doing wrong.</p> <p>The method that throws this exception is <a href="https://github.com/emberjs/data/blob/master/packages/ember-data/lib/adapters/rest_adapter.js#L236-262"><code>sideload</code></a> and checks for the mappings like this:</p> <pre><code>sideload: function (store, type, json, root) { var sideloadedType, mappings, loaded = {}; loaded[root] = true; for (var prop in json) { if (!json.hasOwnProperty(prop)) { continue; } if (prop === root) { continue; } sideloadedType = type.typeForAssociation(prop); if (!sideloadedType) { mappings = get(this, 'mappings'); Ember.assert("Your server returned a hash with the key " + prop + " but you have no mappings", !!mappings); //... </code></pre> <p>This call <code>sideloadedType = type.typeForAssociation(prop);</code> returns <code>undefined</code> and then I get the error message. The method <code>typeForAssociation()</code> checks for the for <code>'associationsByName'</code> key which returns an empty <code>Ember.Map</code>. </p> <p>Still no solution for this at the moment.</p> <p><em><strong>By the way...</em></strong></p> <p>My action is now like this:</p> <pre><code> // GET api/genres public object GetGenres() { return new { genres = context.Genres.AsQueryable() }; } // GET api/genres //[Queryable] //public IQueryable<Genre> GetGenres() //{ // return context.Genres.AsQueryable(); //} </code></pre> <p>I had to remove the original implementation which gets serialized by <a href="http://json.codeplex.com/">json.NET</a> as I could not find config options to produce a json output as Ember-Data expects ( as in <code>{resource_name : [json, json,...]}</code>). Side effect of this is that I've lost built-in OData support, but I'd like to keep it. Does anyone know how could I configure it to produce different json for a collection? </p>

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