How to use same variable across various controllers - ruby on rails

I am using ruby 2.3.1 and rails 3.2.1. I need to initialize a variable called has_sub_menu = false in application controller.

In my application i am using more than 30 controllers and only two controllers contains sub-menu, so i need to assign has_sub_menu = true to these controllers to validate it in layout file.

This is my application.rb

has_sub_menu = false

some_controller01.rb

has_sub_menu = true

some_controller02.rb

has_sub_menu = true

I tried like this in layout.rb,

if controller.has_sub_menu == true
  show_menu_items
end

show_menu_items will be available in that two controller and currently i am not able to access the has_sub_menu value in layout file

I know in c# I can declare the variable as static and access it in any file using object.

Like wise how can i declare a variable in application controller and assign different value to that variable in other two controller and I need to access that value in layout.rb file for sub-menu validation.