rails-engine-example.rb

# engines file strucuture at CD
# each stuff should be namespaced with, for example, `my_engine`
- engines
  + my_engine
    + app
      + assets
        + images
          + my_engine
              image.png
        + javascripts
          + my_engine
              application.coffee
        + stylesheets
          + my_engine
              application.sass
      + controllers
        + my_engine
            application_controller.rb
            registration_controller.rb
      + models
        + my_engine
            registration.rb
            bank_account.rb
      + services
        + my_engine
            service1.rb
            service2.rb
      + helpers
        + my_engine
            application_helper.rb
      + views
        + my_engine
          + registration
              show.html.slim
              apply.html.slim
    + lib
      + my_engine
          engine.rb
          version.rb
          hash_digger.rb # for example
          <another files that we have at lib folder in spacq>
      my_engine.rb
    + config
        routes.rb
    Gemfile
    my_engine.gemspec

##################
### File contents
###################

# Gemfile at CD
gem 'my_engine', '~> 1.0.0', path: 'engines/my_engine'

# engines/my_engine/my_engine.gemspec
$:.push File.expand_path('../lib', __FILE__)

require 'my_engine/version'

Gem::Specification.new do |s|
  s.name        = 'my_engine'
  s.version     = MyEngine::VERSION
  s.authors     = ['OppLoans']
  s.email       = %w()
  s.homepage    = 'https://github.com/Opploans/F'
  s.summary     = 'Engine provide registration process'
  s.description = 'Engine provide registration process'

  s.files = Dir['{app,config,lib}/**/*']

  s.add_dependency 'rails'
  # other dependencies or development dependencies
end

# engines/my_engine/Gemfile
source 'http://rubygems.org'

gemspec

# engines/my_engine/lib/my_engine.rb
module MyEngine
end

# engines/my_engine/lib/my_engine/version.rb
module MyEngine
  VERSION = '1.0.0'
end

# engines/my_engine/lib/my_engine/engine.rb
module MyEngine
  class Engine < Rails::Engine
    isolate_namespace MyEngine

    paths = Dir["#{config.root}/lib/"]
    paths << "#{config.root}/app/services"

    config.autoload_paths   += paths
    config.eager_load_paths += paths

    initializer :asset_precompile_paths do |app|
      app.config.assets.precompile += %w(
        my_engine/application.js
        my_engine/application.css
        my_engine/another.js
      )
    end

    # to initialize something before engine starts (edge cases)
    config.to_prepare do
      require 'my_engine/hash_digger'
    end
  end
end

# engines/my_engine/config/routes.rb
MyEngine::Engine.routes.draw do
  resource :registration, only: :show
end

# mounting engine at CD routes
# config/routes.rb
Rails.application.routes.draw do
  # ...
  mount MyEngine::Engine => '/register', as: :my_engine
end

# engines/my_engine/app/controllers/my_engine/application_controller.rb
module MyEngine
  class ApplicationController < ApplicationController

  end
end

# engines/my_engine/app/controllers/my_engine/registration_controller.rb
module MyEngine
  class RegistrationController < MyEngine::ApplicationController

  end
end