Untitled

I want to create a method that will be available in all controllers, and views
def categories
  @categories = Category.all
end

def list
  categories
  @products = Product.order('title').page(params[:page]).per(4)
end

helper_method :my_method

module ApplicationHelper
  def get_all_categories
     @categories = Category.all
  end
end

<% Category.all.each do |category| %>
     <% do stuff to display all categories %>
<% end %>