Ruby gem method only available in controller? If so, how to make it available in other files?

Question

I was under the impression that a gem's methods can be accessed anywhere in the Rails app once it's been installed with bundler. But is this not the case? I'm confused because a method accessible in the controller isn't recognised when moved outside the file. Is there some way I could require the gem to run the code below in the command file instead of the controller ?

I'm using an authentication gem called sorcery to implement an OAuth login system. There are some methods like login_from(provider) that the gem provides, which can be accessed from my controller just fine.

# app/controllers/oauths_controller.rb
class OauthsController < ApplicationController
  skip_before_action :require_login

  def callback
    provider = params[:provider]
    if @user = login_from(provider)
    # method continues
  end

However, we're trying to take a command-query separation approach in our app, so I tried moving this process containing login_from(provider) method to a different file called app/commands/authentication/login_command.rb . This resulted in the method not being recognised:

NoMethodError (undefined method 'login_from' for #<Authentication::LoginCommand:>)

Thanks in advance.

Answer 1

I was under the impression that a gem's methods can be accessed anywhere in the Rails app once it's been installed with bundler.

That would be an incorrect impression.

As you can see, Sorcery::Engine causes ActionController::Base to include methods defined in Sorcery::Controller , here:

require 'sorcery'
require 'rails'

module Sorcery
  # The Sorcery engine takes care of extending ActiveRecord (if used) and ActionController,
  # With the plugin logic.
  class Engine < Rails::Engine
    config.sorcery = ::Sorcery::Controller::Config

    initializer 'extend Controller with sorcery' do
      # TODO: Should this include a modified version of the helper methods?
      if defined?(ActionController::API)
        ActionController::API.send(:include, Sorcery::Controller)
      end

      if defined?(ActionController::Base)
        ActionController::Base.send(:include, Sorcery::Controller)
        ActionController::Base.helper_method :current_user
        ActionController::Base.helper_method :logged_in?
      end
    end
  end
end

Sorcer::Controller in turn, includes a series of submodules:

module Sorcery
  module Controller
    def self.included(klass)
      klass.class_eval do
        include InstanceMethods
        Config.submodules.each do |mod|
          # FIXME: Is there a cleaner way to handle missing submodules?
          # rubocop:disable Lint/HandleExceptions
          begin
            include Submodules.const_get(mod.to_s.split('_').map(&:capitalize).join)
          rescue NameError
            # don't stop on a missing submodule.
          end
          # rubocop:enable Lint/HandleExceptions
        end
      end
      Config.update!
      Config.configure!
    end

    ...
  end
end

One of these submodules is Sourcery::Controller::Submodules::External which, when included, also includes Sourcery::Controller::Submodules::External::InstanceMethods , here:

module Sorcery
  module Controller
    module Submodules
      # This submodule helps you login users from external auth providers such as Twitter.
      # This is the controller part which handles the http requests and tokens passed between the app and the @provider.
      module External
        def self.included(base)
          base.send(:include, InstanceMethods)
          ...
        end
      end
    end
  end
end

And, InstanceMethods contains the method login_from , here:

module Sorcery
  module Controller
    module Submodules
      # This submodule helps you login users from external auth providers such as Twitter.
      # This is the controller part which handles the http requests and tokens passed between the app and the @provider.
      module External
        def self.included(base)
          base.send(:include, InstanceMethods)

        module InstanceMethods
          protected

          ...

          # tries to login the user from provider's callback
          def login_from(provider_name, should_remember = false)
            sorcery_fetch_user_hash provider_name

            return unless (user = user_class.load_from_provider(provider_name, @user_hash[:uid].to_s))

            # we found the user.
            # clear the session
            return_to_url = session[:return_to_url]
            reset_sorcery_session
            session[:return_to_url] = return_to_url

            # sign in the user
            auto_login(user, should_remember)
            after_login!(user)

            # return the user
            user
          end

          ...
        end
      end
    end
  end
end

Soooo, that's a long way of saying that login_from is defined as a protected instance method on classes that inherit from ActionController::Base and is not defined as an instance method on classes that DO NOT inherit from ActionController::Base which is why you're getting the NoMethodError .

Is there some way I could require the gem to run the code below in the command file instead of the controller?

Maybe. Maybe not. As you can see, login_from is using other sorcery methods and methods inherited from ActionController::Base . So, you would need to make sure all of those methods are available in Authentication::LoginCommand in order for login_from to behave appropriately.