Add custom actions and buttons

ActiveAdmin.register Post do
  # Collection methods
  # published_items_admin_post_(path|url)
  # /admin/post/published_items
  collection_action :published_items do
    @collection = Post.published
    column(:created_at)
    column(:author_name)
    column(:published_at)
    column(:title) { |resource| resource.truncate(100) }
  end

  # Member methods
  # publish_admin_post_(path|url)
  # /admin/post/:id/publish
  member_action :publish do
    # your normal action code
    Post.find(params[:id]).publish!
    redirect_to(:back)
  end
  
  # Buttons on the top right bar, next to the "New #{model_name}" button.
  # show this button only at :published_items action
  action_item :only => :published_items do
    link_to "button label", action_path(resource)
  end
end