title: Serialize and deserialize ActiveRecord model with children
body: <p>Form has many entries. To serialize form and it's entries I use:</p>
  
  <pre><code>json = @form.to_json( { :only =&gt; Form.accessible_attributes.to_a, :include =&gt; {:entries =&gt; {:only =&gt; Entry.accessible_attributes.to_a}}})
  </code></pre>
  
  <p>Form and entries attributes can be modified or deleted while they are in JSON.</p>
  
  <p>To deserialize I use (but not working) :</p>
  
  <pre><code>@form = @form.from_json(json)
  @form.save
  </code></pre>
  
  <p>How to save entries at once with form?</p>