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Diffstat (limited to 'guides/source/initialization.md')
| -rw-r--r-- | guides/source/initialization.md | 53 |
1 files changed, 33 insertions, 20 deletions
diff --git a/guides/source/initialization.md b/guides/source/initialization.md index 9fcd530183..91d12b4432 100644 --- a/guides/source/initialization.md +++ b/guides/source/initialization.md @@ -7,14 +7,17 @@ as of Rails 4. It is an extremely in-depth guide and recommended for advanced Ra After reading this guide, you will know: * How to use `rails server`. +* The timeline of Rails' initialization sequence. +* Where different files are required by the boot sequence. +* How the Rails::Server interface is defined and used. -------------------------------------------------------------------------------- This guide goes through every method call that is required to boot up the Ruby on Rails stack for a default Rails 4 application, explaining each part in detail along the way. For this -guide, we will be focusing on what happens when you execute +rails -server+ to boot your app. +guide, we will be focusing on what happens when you execute `rails server` +to boot your app. NOTE: Paths in this guide are relative to Rails or a Rails application unless otherwise specified. @@ -26,7 +29,7 @@ quickly. Launch! ------- -Now we finally boot and initialize the app. It all starts with your app's +Let's start to boot and initialize the app. It all begins with your app's `bin/rails` executable. A Rails application is usually started by running `rails console` or `rails server`. @@ -36,8 +39,8 @@ This file is as follows: ```ruby #!/usr/bin/env ruby -APP_PATH = File.expand_path('../../config/application', __FILE__) -require File.expand_path('../../config/boot', __FILE__) +APP_PATH = File.expand_path('../../config/application', __FILE__) +require_relative '../config/boot' require 'rails/commands' ``` @@ -57,7 +60,8 @@ require 'bundler/setup' if File.exists?(ENV['BUNDLE_GEMFILE']) In a standard Rails application, there's a `Gemfile` which declares all dependencies of the application. `config/boot.rb` sets `ENV['BUNDLE_GEMFILE']` to the location of this file. If the Gemfile -exists, `bundler/setup` is then required. +exists, then `bundler/setup` is required. The require is used by Bundler to +configure the load path for your Gemfile's dependencies. A standard Rails application depends on several gems, specifically: @@ -213,12 +217,12 @@ With the `default_options` set to this: ```ruby def default_options { - :environment => ENV['RACK_ENV'] || "development", - :pid => nil, - :Port => 9292, - :Host => "0.0.0.0", - :AccessLog => [], - :config => "config.ru" + environment: ENV['RACK_ENV'] || "development", + pid: nil, + Port: 9292, + Host: "0.0.0.0", + AccessLog: [], + config: "config.ru" } end ``` @@ -251,9 +255,9 @@ set earlier) is required. ### `config/application` -When `require APP_PATH` is executed, `config/application.rb` is loaded. -This file exists in your app and it's free for you to change based -on your needs. +When `require APP_PATH` is executed, `config/application.rb` is loaded (recall +that `APP_PATH` is defined in `bin/rails`). This file exists in your application +and it's free for you to change based on your needs. ### `Rails::Server#start` @@ -346,7 +350,7 @@ end The interesting part for a Rails app is the last line, `server.run`. Here we encounter the `wrapped_app` method again, which this time we're going to explore more (even though it was executed before, and -thus memorized by now). +thus memoized by now). ```ruby @wrapped_app ||= build_app app @@ -373,7 +377,7 @@ The `options[:config]` value defaults to `config.ru` which contains this: ```ruby # This file is used by Rack-based servers to start the application. -require ::File.expand_path('../config/environment', __FILE__) +require ::File.expand_path('../config/environment', __FILE__) run <%= app_const %> ``` @@ -388,7 +392,7 @@ app = eval "Rack::Builder.new {( " + cfgfile + "\n )}.to_app", The `initialize` method of `Rack::Builder` will take the block here and execute it within an instance of `Rack::Builder`. This is where the majority of the initialization process of Rails happens. The `require` line for `config/environment.rb` in `config.ru` is the first to run: ```ruby -require ::File.expand_path('../config/environment', __FILE__) +require ::File.expand_path('../config/environment', __FILE__) ``` ### `config/environment.rb` @@ -443,7 +447,9 @@ I18n and Rails configuration are all being defined here. ### Back to `config/environment.rb` -When `config/application.rb` has finished loading Rails, and defined +The rest of `config/application.rb` defines the configuration for the +`Rails::Application` which will be used once the application is fully +initialized. When `config/application.rb` has finished loading Rails and defined the application namespace, we go back to `config/environment.rb`, where the application is initialized. For example, if the application was called `Blog`, here we would find `Blog::Application.initialize!`, which is @@ -471,6 +477,13 @@ traverses all the class ancestors looking for an `initializers` method, sorting them and running them. For example, the `Engine` class will make all the engines available by providing the `initializers` method. +The `Rails::Application` class, as defined in `railties/lib/rails/application.rb` +defines `bootstrap`, `railtie`, and `finisher` initializers. The `bootstrap` initializers +prepare the application (like initializing the logger) while the `finisher` +initializers (like building the middleware stack) are run last. The `railtie` +initializers are the initializers which have been defined on the `Rails::Application` +itself and are run between the `bootstrap` and `finishers`. + After this is done we go back to `Rack::Server` ### Rack: lib/rack/server.rb @@ -546,7 +559,7 @@ def self.run(app, options={}) else server.register('/', Rack::Handler::Mongrel.new(app)) end - yield server if block_given? + yield server if block_given? server.run.join end ``` |