Set filter before_action for ActiveAdmin controller

You can access the controller from within the controller do ... end DSL:

ActiveAdmin.register User do

  before_action :set_product, only: [:show, :edit, :update, :destroy]

  controller do
    def set_product
      @product = Product.find_by_name(params[:name])
    end
  end

end

You can store it in the config: config/initializers/active_admin.rb

ActiveAdmin.setup do |config|
  def do_something_awesome
  end

  config.before_action :do_something_awesome      
end