Multi-tenancy set up using Rails + Houser

application.rb

# config/application.rb
require './app/middleware/company_middleware.rb'

module MyApp
  class Application < Rails::Application
    config.middleware.use 'Houser', class_name: 'Company'
    config.middleware.use 'CompanyMiddleware'
  end
end

application_controller.rb

# app/controllers/application_controller.rb
class ApplicationController < ActionController::Base
  expose(:current_company) { env['X-Houser-Object'] }

  before_filter :within_company_context,           if: :devise_controller?
  before_filter :set_default_subdomain
  
  
  def set_default_subdomain
    SetUrlOptions.call current_company, default_url_options
  end

  def within_company_context
    return if current_company.present?

    render text: 'Not Found', status: 404
  end
end

company_middleware.rb

# app/middleware/company_middleware.rb
class CompanyMiddleware
  def initialize(app)
    @app = app
  end

  def call(env)
    unless env['PATH_INFO'][%r{/assets/}]
      current_company        = find_company_by_domain env
      env['X-Houser-Object'] = current_company unless current_company.nil?
    end

    app.call(env)
  end

  private

  attr_reader :app

  def find_company_by_domain(env)
    return nil unless env['HTTP_HOST']

    Company.find_by domain: env['HTTP_HOST']
  end
end

development.rb

# config/environments/development.rb

MyApp::Application.configure do
  ENV['DEFAULT_HOST'] ||= 'myapp.dev'
end

production.rb

# config/environments/production.rb

MyApp::Application.configure do
  ENV['DEFAULT_HOST'] ||= 'myapp.com'
end

set_url_options.rb

# app/lib/set_url_options.rb
class SetUrlOptions
  def self.call(current_company, *option_hashes)
    option_hashes += [
      Rails.application.config.action_mailer.default_url_options,
      ActionMailer::Base.default_url_options,
      Rails.application.routes.default_url_options
    ]

    option_hashes.each { |options| new(current_company, options).call }
  end

  def initialize(current_company, options)
    @current_company, @options = current_company, options
  end

  def call
    if current_company.nil?
      options.delete :subdomain
      options[:host] = ENV['DEFAULT_HOST']
    elsif current_company.domain.blank?
      options[:subdomain] = current_company.subdomain
      options[:host]      = ENV['DEFAULT_HOST']
    else
      options.delete :subdomain
      options[:host] = current_company.domain
    end
  end

  private

  attr_reader :current_company, :options
end