Quick and simple example of how output active menu class for Rails applications

example.rb

# Example:
#
# Let's say we're are accessing a new form to create a Post, probably
# our page will be rendered by PostsController and new action:
class PostsController < ApplicationController
  def new
    @post = Post.new
    
    render :new
  end
end

# If we want to add class `active` into our menu view we need to
# specify when it should be active for the active_menu_class helper:
#
# app/views/posts/new.html.erb
<ul id="menu">
  <li class="<%= active_menu_class('posts', 'new') %>">Novo Post</li>
</ul>

menu_helper.rb

module MenuHelper
  # It's best to not use methods with question mark because they suggest
  # a return of a boolean (true or false)
  #
  # Rails give us two helper that tell us which controller and action
  # are currently being accessed.
  def active_menu_class(active_controller, active_action)
    # Could be 'active' instead :active, I just prefer to use a Symbol
    # over String
    :active if action_controller == controller_name && active_action == action_name
  end
end