Began adding the relationships collection to the Dataset model. Ticket …

…#5

lib/model.js

@@ -71,6 +71,12 @@ CKAN.Model = function ($, _, Backbone, undefined) {
   // Model objects
   Model.Dataset = Model.Base.extend({
     constructor: function Dataset() {
+      // Define an key/model mapping for child relationships. These will be
+      // managed as a Backbone collection when setting/getting the key.
+      this.children = {
+        resources: Model.Resource,
+        relationships: Model.Relationship
+      };
       Model.Base.prototype.constructor.apply(this, arguments);
     },
 
@@ -81,12 +87,9 @@ CKAN.Model = function ($, _, Backbone, undefined) {
     set: function (attributes, options) {
       var resources, validated;
 
-      // If not yet defined set the resources collection. This will be done when
+      // If not yet defined set the child collections. This will be done when
       // set is called for the first time in the constructor.
-      if (!this.get('resources')) {
-        this.attributes.resources = new Backbone.Collection();
-        this.attributes.resources.model = Model.Resource;
-      }
+      this._createRelationships();
 
       if (attributes && attributes.resources) {
         if (!(attributes.resources instanceof Backbone.Collection)) {
@@ -105,6 +108,18 @@ CKAN.Model = function ($, _, Backbone, undefined) {
       return validated;
     },
 
+    // Checks to see if our model instance has Backbone collections defined for
+    // child keys. If they do not exist it creates them.
+    _createRelationships: function () {
+      _.each(this.children, function (Model, key) {
+        if (!this.get(key)) {
+          this.attributes[key] = new Backbone.Collection();
+          this.attributes[key].model = Model;
+        }
+      }, this);
+      return this;
+    },
+
     // Manages the one to many relationship between resources and the dataset.
     // Accepts an array of Resources (ideally model instances but will convert
     // object literals into resources for you). New models will be added to the

test/model-test.js

@@ -73,13 +73,13 @@ test(".set({resources: []})", function () {
       resources = dataset.get('resources'),
       newResources = new Backbone.Collection();
 
+  this.spy(dataset, '_createRelationships');
   this.spy(dataset, '_updateResources');
 
-  equals(resources.constructor, Backbone.Collection, 'The resources attribute should be a Backbone collection');
-  equals(resources.model, CKAN.Model.Resource, 'Should create Resource instances');
   equals(resources.length, 0, 'The resources collection should be empty');
 
   dataset.set({});
+  equals(dataset._createRelationships.callCount, 1, 'Expected dataset._createRelationships() to have been called');
   ok(!dataset._updateResources.calledOnce, 'Expected collection._updateResources() NOT to have been called');
 
   dataset.set({resources: newResources});
@@ -93,6 +93,20 @@ test(".set({resources: []})", function () {
   ok(dataset._updateResources.calledTwice, 'Expected collection._updateResources() to have been called');
 });
 
+test("._createRelationships()", function () {
+  var dataset = new CKAN.Model.Dataset(), attrs, returned;
+  attrs = dataset.attributes = {};
+
+  returned = dataset._createRelationships();
+
+  ok(dataset, returned, 'Expected it to return itself');
+  equals(attrs.resources.constructor, Backbone.Collection, 'The resources attribute should be a Backbone collection');
+  equals(attrs.resources.model, CKAN.Model.Resource, 'Should create Resource instances');
+
+  equals(attrs.relationships.constructor, Backbone.Collection, 'The resources attribute should be a Backbone collection');
+  equals(attrs.relationships.model, CKAN.Model.Relationship, 'Should create Resource instances');
+});
+
 test("._updateResources()", function () {
   var dataset = new CKAN.Model.Dataset(),
       resources = dataset.get('resources'),