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POProper Handling of hasMany/belongsTo in Ember Data with Rails Persistence
 

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  1. POProper Handling of hasMany/belongsTo in Ember Data with Rails Persistence
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    <p>I have an Ember.js app (1.0.0-rc.3) using Ember Data (Rev 12) to persist to a Rails backend. On the client side, I have two models that have a one-to-many relationship:</p> <pre><code>App.Child = DS.Model.extend( name: DS.attr('string') parent: DS.belongsTo('App.Parent') App.Parent = DS.Model.extend( name: DS.attr('string') children: DS.hasMany('App.Child') ) </code></pre> <p>I have configured my store to expect JSON from Rails that embeds relationships rather than side-loading them:</p> <pre><code>App.Store = DS.Store.extend( revision: 12 adapter: DS.RESTAdapter.extend(serializer: DS.RESTSerializer.extend(init: -&gt; @_super() @map "App.Child", parents: embedded: "always" )) ) </code></pre> <p>And then I have a form for creating a new <code>App.Child</code> record. In the childNewController for the new <code>App.Child</code> form view, I create a new <code>App.Child</code> and a new <code>App.Parent</code> as follows:</p> <pre><code>@transaction = @get('store').transaction() @set('content', @transaction.createRecord(App.Child, {})) @set('content.parent', @transaction.createRecord(App.Parent, {})) </code></pre> <p>I have textfields bound to the various attributes of both child and parent. When I click the save button on the form, an action in the childNewController commits the changes with <code>@transaction.commit()</code>.</p> <p>THE PROBLEM</p> <p>When the transaction is committed, Rails receives two JSON POST requests—one to the ParentController with JSON that looks like:</p> <pre><code>{"parent"=&gt;{"name"=&gt;"William"}} </code></pre> <p>...and a second POST to the ChildController with JSON that looks like: </p> <pre><code>{"child"=&gt;{"name"=&gt;"Henry", "parent"=&gt;{"name"=&gt;"William"}}} </code></pre> <p>Now the Rails ChildController and ParentController are both trying to save the new parent. </p> <p>Ideally, the request to the ParentController would go away, since I don't want it, and it lacks sufficient information to establish a relationship with the child. I would simply ignore the request to ParentController, but Ember Data is expecting a response from the server. </p> <p>Another option would be to let ParentController save the new parent, and then ChildController could look up the newly-saved parent record and create the linkage to the new child record. The problem is that the sequence of the two requests is unpredictable. </p> <p>Because of this sequencing issue, I tried putting <code>Parent.find_or_create_by_name(parent_name)</code> in both Rails controllers, on the theory that if one controller has already created the new parent, the other would only execute a lookup of that new parent record. However, this resulted in duplicate parent records!</p> <p>I'm really at a loss to understand why Ember Data insists on pushing duplicate JSON representations of the parent to the backend. I'm sure it's a simple configuration error on my part.</p> <p><strong>Update</strong></p> <p>I found an acceptable workaround for now by chaining the commits:</p> <pre><code>newParent = @transaction.createRecord(App.Parent, {name: parentName}) currentChild = @get('content') # we assigned a new App.Child to the childNewController in the new child route's controller setup currentStore = @get('store') newParent.one('didCreate', this, -&gt; now = new Date() transaction = currentStore.transaction() transaction.add currentChild transaction.commit() transaction = null ) newParent.get('transaction').commit() @transaction = null </code></pre> <p>Is there a better way to do this?</p>
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      1. POProper Handling of hasMany/belongsTo in Ember Data with Rails Persistence
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    1. COI am trying something similar, just the other way around, so I have the parent-model and want the child-model included. I am getting nothing to work so far. And furthermore I am trying your not updated approach and don't even get the parent model to be included in my child model. Did you make any progress here?
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      1. USMarkus
 

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A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

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