application_controller.rb

class ApplicationController < ActionController::Base

  # stuff

  private

  # These groups are equivalent:
  #
  #   render action: :new, locals: { item: x }
  #   render :new, locals: { item: x }
  #   locals :new, item: x
  #
  #   render locals: { item: x }
  #   locals item: x
  #
  def locals(action = nil, hash)
    render action: action, locals: hash
  end
end