rails_admin.rb

config.actions do
    # root actions
    dashboard                     # mandatory
    # collection actions 
    index                         # mandatory
    new
    export
    bulk_delete
    # member actions
    show
    edit
    delete
    history_show
    show_in_app

    collection :publish do

    end
end

rails_admin_publish.rb

# in lib/rails_admin_publish.rb

require 'rails_admin/config/actions'
require 'rails_admin/config/actions/base'

module RailsAdminPublish
end

module RailsAdmin
  module Config
    module Actions
      class Publish < RailsAdmin::Config::Actions::Base
      	
      	register_instance_option :collection do
          true
        end

	register_instance_option :bulkable? do
          true
        end

	register_instance_option :controller do
            Proc.new do
		@object.update_attribute(:published, true)
		flash[:notice] = "You published: #{@object.title}."

		redirect_to back_or_index
            end
	end
      end
    end
  end
end