How could I understand the code? I read it, and read it, and I read it I spent too much time reading and learning the code I don't want all other contributors to repeat that waste of time
I spent too much time reading and learning the code Because I learned it without a guide I wish I had a good guide like "Ruby Hacking Guide" by Minero Aoki So I'm speaking and writing
gem-src (a social coder's best friend) Usage % gem i rails #=> automatically git-clone You no more need to memorize the gem author name, or search in GitHub!
rails.gemspec s.add_dependency 'activesupport', version s.add_dependency 'actionpack', version s.add_dependency 'actionview', version s.add_dependency 'activemodel', version s.add_dependency 'activerecord', version s.add_dependency 'actionmailer', version s.add_dependency 'railties', version
rails.gemspec s.add_dependency 'activesupport', version s.add_dependency 'actionpack', version s.add_dependency 'actionview', version s.add_dependency 'activemodel', version s.add_dependency 'activerecord', version s.add_dependency 'actionmailer', version s.add_dependency 'railties', version
Summary: Let's start reding! rails gem is a meta package that depends on the whole MVC components There's a gem that is not included in any of the MVC components, which is called railties
Railroad tie "a rectangular support for the rails in railroad tracks" "Generally laid perpendicular to the rails" "Railroad ties were traditionally made of wood"
Each gems has their own Railtie inheriting Rails::Railtie module ActionMailer class Railtie < Rails::Railtie module ActionController class Railtie < Rails::Railtie module ActionDispatch class Railtie < Rails::Railtie module ActionView class Railtie < Rails::Railtie module ActiveModel class Railtie < Rails::Railtie module ActiveRecord class Railtie < Rails::Railtie
What's written in a Railtie? (active_model/railtie.rb) require "active_model" require "rails" module ActiveModel class Railtie < Rails::Railtie # :nodoc: config.eager_load_namespaces << ActiveModel initializer "active_model.secure_password" do ActiveModel::SecurePassword.min_cost = Rails.env.test? end ennd
One more thing about Rails::Railtie Prohibited to be instantiated from outside self.instance returns the singleton instance Why is it a class despite you can't instantiate?
What's gonna happen when Rails::Railtie is inherited? (rails/railtle.rb) module Rails class Railtie class << self def inherited(base) unless base.abstract_railtie? subclasses << base ennnnnd
rails/commands/server.rb module Rails class Server < ::Rack::Server def initialize(*) super ENV["RAILS_ENV"] ||= options[:environment] end def start super ennnd
I'm not gonna do rack code reading here But method calls go on like start => wrapped_app => app => build_app_and_options_from_ con g => Rack::Builder.parse_ le => Rack::Builder.new_from_string
Rails.root/con g.ru # This file is used by Rack-based servers to start the application. puts caller require ::File.expand_path('../config/environment', __FILE__) run Rails.application
rails/all.rb require "rails" %w( active_record action_controller action_view action_mailer rails/test_unit sprockets ).each do |framework| begin require "#{framework}/railtie" rescue LoadError end end
What's in the initializers collection? Instances of Rails::Initializable::Initializer Each Initializer just holds a Proc instance (and a name and options) given to Rails::Railtie::Initializable.initial ize method call
Summary: How Rails server boots Require all gems in the Gem le (bundler) Load all Railties and Engines (con g/ application.rb) De ne YourApp::Application inheriting Rails::Application (con g/application.rb) Run Railtie#initializer de ned in each Railtie, Engine, and Application Load each Engine's load_path and routes, then load con g/initializers/* Run Rails.application (con g.ru) => The next chapter
Rails::Engine is also a Rack app (railties/lib/rails/engine.rb) module Rails class Engine ... def call(env) env.merge!(env_config) if env['SCRIPT_NAME'] env.merge! "ROUTES_#{routes.object_id}_SCRIPT_NAME" => env['SCRIPT_NAME'].dup end app.call(env) ennnd
What is con g.middleware? (rails/engine/con guration.rb) module Rails class Engine class Configuration < ::Rails::Railtie::Configuration def middleware @middleware ||= Rails::Configuration::MiddlewareStackProxy.new ennnnd
Summary: Building middleware stack The Rack server calls `Rails.application.call` It calls the Rails default middleware stack and the endpoint The endpoint is "routes"
Rails.application.routes is also a Rack app (action_dispatch/routing/route_set.rb) module ActionDispatch module Routing class RouteSet ... def call(env) @router.call(env) ennnnd
Rails.application.routes is also a Rack app This is how Rails.application's endpoint accepts the Rack request But for now, let's go back to routes.draw DSL
What is endpoint? (action_dispatch/routing/mapper.rb) module ActionDispatch module Routing class Mapper class Mapping ... def endpoint to.respond_to?(:call) ? to : dispatcher ennnnnnd
Summary: Routes Rails.application.routes is a Rack app Each routes' endpoint is a Rack app Each controller's each action is a Rack app e.g. 'foo#bar' becomes a Rack app generated by FooController.action('bar') Everything is a Rack app
Creating a Request object, and adding a Proc to the stack (action_controller/metal.rb) module ActionController class Metal < AbstractController::Base def self.action(name, klass = ActionDispatch::Request) middleware_stack.build(name.to_s) do |env| new.dispatch(name, klass.new(env)) end ennnd
Controller#process (abstract_controller/base.rb) module AbstractController class Base def process(action, *args) ... process_action(action_name, *args) end private def process_action(method_name, *args) send_action(method_name, *args) end alias send_action send ennnd
Summary: Controllers and actions The request goes to FooController.action('bar') FooController.action('bar') sets the Rails Request and Response objects to the controller instance Then call goes to FooController#bar via `send` call
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