title: ActiveAdmin, Formtastic, and Paperclip: Not Rendering File Dialog
body: <p>I'm implementing a generic media gallery using Ruby on Rails. I've chosen ActiveAdmin to handle the administration portion of my task and it's worked well so far, except for one thing: It's not displaying the "Choose file" dialog as intended.</p>
  
  <p>This is a form for my "Media" section of ActiveAdmin. I have a model called "Medium" with the following fields (in addition to <code>id</code> and <code>timestamp</code>:</p>
  
  <ul>
  <li><code>asset_file_name</code></li>
  <li><code>asset_file_size</code></li>
  <li><code>asset_content_type</code></li>
  <li><code>asset_updated_at</code></li>
  </ul>
  
  <p>My <code>Medium</code> model looks like this:</p>
  
  <pre><code>class Medium &lt; ActiveRecord::Base
    has_and_belongs_to_many :galleries
    has_and_belongs_to_many :entities
  
    has_attached_file :asset, :styles =&gt; { :medium =&gt; "300x300&gt;", :thumb =&gt; "100x100&gt;" }
  
    attr_accessible :asset
  end
  </code></pre>
  
  <p>And I'm adding it to the ActiveAdmin form like this:</p>
  
  <pre><code>  form :html =&gt; { :enctype =&gt; "multipart/form-data" } do |f|  
      f.input :asset, :as =&gt; :file
      f.buttons
    end
  </code></pre>
  
  <p>Here's a screencap of my ActiveAdmin page:
  <img src="https://i.stack.imgur.com/reoC0.png" alt="New Medium"></p>
  
  <p>I see nothing wrong with how I'm implementing this. I've read that Formtastic has  historically had issues with paperclip and I'm not averse to switching to attachment_fu or any other suitable solutions.</p>
  
  <p>I should also note: I know that I can add in a custom partial. It's not my ideal solution, as I'd like to keep everything in the Formtastic DSL. </p>
  
  <p>Thanks!</p>