ApplicationHelper not loaded in Rails 4 engine

Question

Long time reader of SO here. I'm working on a Rails Engine. The big picture problem is that I get a NoMethodError on a helper method living in my Engine's ApplicationHelper. This is for work so I'm going to call the engine Blorge.

I have my helper method that is causing issues anywhere it is called. The Helper method is returning a NoMethodError. I thought maybe I needed to manually add helper Blorge::ApplicationHelper to Blorge::ApplicationController but the issue is still happening.

Am I missing something fundamental about Engines here?

Here is some actual code to give you a better idea of what I'm looking at.

index_header partial

app/views/blorge/shared/_index_header.html.erb

# require_locals is the helper method in question here
<% require_locals ['title'], local_assigns %>
<% title = title.pluralize %>

<section class="main_content-header">
  <div class="main_content-header-wrapper">
    <%= content_tag :h1, title %>

    <div class="main_content-header-save">
      <%= link_to "New #{title.singularize}", @new_path, class: "add-button" %>
    </div>
  </div>
</section>

Pages#home view

app/views/blorge/pages/home.html.erb

<%= render 'blorge/shared/index_header', title: "Welcome, #{current_user.full_name}" %>

...

Engine Application Helper

app/helpers/blorge/application_helper.rb

module Blorge
  module ApplicationHelper

    def require_locals(local_array, local_assigns)
      local_array.each do |loc|
        raise "#{loc} is a required local, please define it when you render this partial" unless local_assigns[loc.to_sym].present?
      end
    end

  end
end

Engine Pages Controller

app/controller/blorge/pages_controller.rb

module Blorge
  class PagesController < ApplicationController

    def home
    end

  end
end

Engine Application Controller

app/controllers/blorge/application_controller.rb

class Blorge::ApplicationController < ActionController::Base
  helper Blorge::ApplicationHelper

  ...
end

If I restart the server and reload the page, it will usually work just fine, and once it works, the issue doesn't come back for a couple days. After reading Helpers in Rails engine and Rails Engines: Helpers only are reloaded when restarting the server it sounds like I need to include the helper in my application controller with the to_prepare method in my engine.rb file. I am going to try this next but I most want to know if I'm missing something very basic here, If i do just have to add it to engine.rb, can someone explain why?

This might have been too much information, but I'd rather give more than not enough. Thanks in advance.

---

Edit

the fix seems to have been adding the helpers to application controller within engine.rb. I suspected this would be the fix, but I still have no clue why this is. Does anyone know why I should have to do this?

The Solution

config.to_prepare do
  ApplicationController.helper(MyEngineHelper)
end