Overview

This document records the code reading work for Ruby on Rails.

Preparation

1. Create a new project with rails new RailsCodeReading.
2. Add the following to the Gemfile:

gem 'pg'
gem 'pry-rails'
gem 'pry-doc'
gem 'pry-byebug'
gem 'byebug'

3. Run bundle config set path '.bundle', then execute bundle install.
4. Run rails generate controller Example.
5. Implement the index method in the controller:

  def index
    binding.pry
    render json: { message: 'Hello World!' }
  end

6. Set up the routing:

  get "example" => "example#index"

Code Reading

Let's trace how Rails processes requests.

By accessing http://127.0.0.1:3000/example and using pry-backtrace in the console, you can see the stack trace.

Since a lot of output is generated, we can't follow everything, so we'll skip through it.

1. Puma accepts the request and calls the Rails application.

• puma/puma - lib/puma/request.rb#L99
• railties/lib/rails/engine.rb#L536
  • Definition of the Rack API
• rack/rack - lib/rack/sendfile.rb#L113
  • Rack application is executed.

2. Based on the request information, the routing is resolved.

• rails/rails - actionpack/lib/action_dispatch/journey/router.rb#L126
• rails/rails - actionpack/lib/action_dispatch/routing/route_set.rb#L66
  • Calls the processing of the controller that matched the routing.

3. Calls the index of the controller.

• rails/rails - actionpack/lib/action_controller/metal/basic_implicit_render.rb#L7

It was more complex than I imagined, and since I'm not familiar with Ruby, I could only grasp the general idea...

References

• speakerdeck.com - Ruby on Rails Hacking Guide
• magazine.rubyist.net - Trying RubyOnRails 【Part 4】 ActionPack