example.rb

class ApplicationController
  helper_method :current_copywriting

  def current_copywriting
    @current_copywriting ||= Copywriting.find_by_request(request)
  end
end

module SomeHelpers
  def header_text
    current_copywriting ? current_copywriting.header_text : "default text"
  end

  def meta_keywords
    if current_copywriting
      current_copywriting.meta_keywords
    else
      ["default", "keywords"]
    end
  end
end