title: after click on edit button previous uploaded file is not showing on rails form
body: <p>Previous uploaded file/image is not showing on edit form after clicking on the edit button it shows only no file selected, but files are already stored into the database. This is my haml form which is below. </p>
  
  <pre><code>.....
  .....
  
  .field
    = f.label "address_proof"
    = f.file_field :address_proof, :required =&gt; true, :class =&gt;'form- control', placeholder: "upload address proof"
  .field
    = f.label "identity_proof"
    = f.file_field :identity_proof, :required =&gt; true, :class =&gt;'form-control', placeholder: "upload identity proof" 
   %br.actions
    = f.submit 'submit', :class=&gt;"btn waves-effect waves-light", :id=&gt;"validate"
    = link_to 'Cancel', admin_members_path, :class=&gt;"btn white grey-text waves-effect waves-red"
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/T2QZt.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/T2QZt.png" alt="enter image description here"></a></p>