title: How to make new.json.rabl
body: <p>I want to generate new.json.rabl page to create new post
  first of all i created in post folder new.json.rabl file</p>
  
  <pre><code>object @post
  attributes :content, :photo
  </code></pre>
  
  <p>and localhost:3000/post/new.json return </p>
  
  <pre><code>{"post":{"content":null,"photo":null}}
  </code></pre>
  
  <p>how can i send content and photo values to rabl</p>