title: Active Admin Permitted Params
body: <p>Is there a way to tell whether I am in create or edit mode from inside the permit_params block of active admin? I'd like to merge created_by and updated_by when I'd creating a new record. When I'm editing an existing record I only want to merge updated_by.</p>
  
  <p>Here's my code:</p>
  
  <pre><code>ActiveAdmin.register Group do
    menu parent: "Groups", priority: 0
  
    permit_params do
      permitted = [:name, :description, :group_type_id, :owner_user_id]
      permitted.merge!(updated_by: current_admin_user)
      permitted
    end
  </code></pre>
  
  <p>I'd like to say something like:</p>
  
  <pre><code>permitted.merge!(created_by: current_admin_user) if new_record?
  </code></pre>
  
  <p>new_record? is an active admin method but it only seems to work in forms.</p>
  
  <p>Any ideas?</p>