Rails 5 API - error autoloading helper when using the api_only flag

Question

I'm trying to use a module from the folder 'app/helpers/transaction_helper.rb'. (It's important to note that the application is using the api_only flag, and helpers aren't being generated or loaded by default.)

module TransactionHelper
  module Generator
    def self.code_alphanumeric(params)
    end
  end
end

I got this error:

NameError: uninitialized constant TransactionHelper

I tried to add the following line to the application.rb

config.autoload_paths += %W(#{config.root}/app/helpers)

require_relative 'boot'

require "rails"
# Pick the frameworks you want:
require "active_model/railtie"
require "active_job/railtie"
require "active_record/railtie"
require "action_controller/railtie"
require "action_mailer/railtie"
require "action_view/railtie"
require "action_cable/engine"
# require "sprockets/railtie"
require "rails/test_unit/railtie"

# Require the gems listed in Gemfile, including any gems
# you've limited to :test, :development, or :production.
Bundler.require(*Rails.groups)

module SistemaControleContasApi
  class Application < Rails::Application
    config.autoload_paths += %W(#{config.root}/app/helpers)
    # Settings in config/environments/* take precedence over those specified here.
    # Application configuration should go into files in config/initializers
    # -- all .rb files in that directory are automatically loaded.

    # Only loads a smaller set of middleware suitable for API only apps.
    # Middleware like session, flash, cookies can be added back manually.
    # Skip views, helpers and assets when generating a new resource.
    config.api_only = true
  end
end

But this until not work. If I try to put this file in the app/models directory, this work. However, this is not the right local to place a helper.

Could someone help, please?

Answer 1

Normally everything under app is autoloaded by default if you follow the Rails™ naming conventions. See here Docs.

set_autoload_paths: This initializer runs before bootstrap_hook. Adds all sub-directories of app and paths specified by config.autoload_paths, config.eager_load_paths and config.autoload_once_paths to ActiveSupport::Dependencies.autoload_paths.

So in the first step you should remove config.autoload_paths += %W(#{config.root}/app/helpers) from your config.

Then for every module you should create a subfolder.
So for your problem you should put your module under app/modules/transaction_helper/generator.rb

Also you don't need self in a module scope.

---

Personally I would create the helper as follows:

module TransactionHelper
  def generate_alphanumeric_code
     # params are automatically available in helpers.
  end
end

And put it under app/modules/transaction_helper.rb.