Home Rails app fails with "uninitialized constant"
 I could use some help figuring out a problem in a trivial Rails app (version 4, I believe). I'm not familiar with Rails, the app is just part of a Docker/AWS tutorial that I'm stepping through. I need to get it working so the following steps make sense. It's a little surprising that the app gets an error, because I pasted it in directly from the course resources. When I load the main page, I get an error page something like this:  NameError in PagesController#home uninitialized constant PagesController::ThrowJavelinsJob Extracted source (around line #6): @hostname = Socket.gethostname ThrowJavelinsJob.perform_later end def health_check  This is in "./app/controllers/pages_controller.rb" from the root of the application: class PagesController < ApplicationController def home @total_hits = Rails.cache.increment('total_hits') @hostname = Socket.gethostname ThrowJavelinsJob.perform_later end def health_check head :ok end end  In "./app/jobs/throw_javelins_job.rb" is the following: class ThrowJavelinsJob < ActiveJob::Base queue_as :default def perform(*args) sleep 5 javelins_thrown = rand(1..10) Javelin.create!(thrown: javelins_thrown) end end  I did get a hint on gitter that I need to either "autoload" this module or "require" it. I don't know how I would autoload it, but in case making it "require" it would be done by a simple change to existing code, I grepped for "require" in the application code and got this: ./config/application.rb:1:require File.expand_path('../boot', __FILE__) ./config/application.rb:3:require 'rails/all' ./config/application.rb:7:Bundler.require(*Rails.groups) ./config/environment.rb:2:require File.expand_path('../application', __FILE__) ./config/boot.rb:3:require 'bundler/setup' # Set up gems listed in the Gemfile. ./Rakefile:4:require File.expand_path('../config/application', __FILE__) ./config.ru:3:require ::File.expand_path('../config/environment', __FILE__)  So, what would be the most logical change to this existing code to get this to work?