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railtie 负责将所有Rails组件组合绑定粘合到一起

Rails启动过程

config.ru -> environment.rb -> application.rb -> boot.rb

boot.rb

加载Bundler，加载Gemfile所指定的所有gem

application.rb

  1. 通过require 'rails/all'加载Rails环境
  2. Bundler加载运行环境（development, test, production）
  3. 定义Rails工程，并进行初始化设置
module NewApp
  class Application < Rails::Application
    ...
  end
end

environment.rb

通过NewApp::Application.initialize!初始化应用程序

config.ru

通过run Rails.application将应用程序交给Rack并运行

Rails (module)

封装了application,cache,logger三个参数

application为Rails::Application实例

rails new new_app
cd new_app
rails c
Rails.application.class  # => NewApp::Application
Rails.application.is_a?(NewApp::Application)  # => true
def inherited(base)
  raise "You cannot have more than one Rails::Application" if Rails.application
  super
  Rails.application = base.instance
  Rails.application.add_lib_to_load_path!
  ActiveSupport.run_load_hooks(:before_configuration, base.instance)
end

通过上面的代码，NewApp::Application的实例传递给了Rails.application的，而且只允许一个实例

cache为ActiveSupport::Cache::FileStore实例

Rails.cache.class  # => ActiveSupport::Cache::FileStore

cache为ActiveSupport::Logger实例

Rails.logger.class  # => ActiveSupport::Logger

Rails::Railtie (class)

  • include Rails::Initializable
  • 为继承自Railtie的所有class或者module（Rails::Engine和Rails::Application除外）包含了Railtie::Configurable
  • 运用下面的代码，Rails::Railtie记录了所有子类
def subclasses
  @subclasses ||= []
end

def inherited(base)
  unless base.abstract_railtie?
    base.send(:include, Railtie::Configurable)
    subclasses << base
  end
end
  • 用config为每一个Railtie实例储存了Railtie::Configuration实例，用于存储配置
class MyRailtie < Rails::Railtie
  # Customize the ORM
  config.app_generators.orm :my_railtie_orm

  # Add a to_prepare block which is executed once in production
  # and before each request in development
  config.to_prepare do
    MyRailtie.setup!
  end
end
  • 可通过rake_tasks，console，runner，generators加入自己的内容
class MyRailtie < Rails::Railtie
  rake_tasks do
    load "path/to/my_railtie.tasks"
  end
  
  generators do
    require "path/to/my_railtie_generator"
  end
end

Rails::Railtie::Configurable (module)

封装了instance参数，通过method_missing将所有的方法转到instance来调用

Rails::Engine (class)

Rails::Engine is a Rails::Railtie

  • 当定义一个Rails::Engine子类的时候，会调用base.send(:include, Railtie::Configurable)
class MyEngine < Rails::Engine
  config.autoload_paths << File.expand_path("../lib/some/path", __FILE__)
end

  • 而Rails::Railtie::Configurable封装了instance参数，通过method_missing将所有的方法转到instance来调用

  • 当调用config方法时，就会初始化MyEngine，然后转到这个实例(instance)来调用

MyEngine.config # => MyEngine.new.config
MyEngine.config.class # => Rails::Engine::Configuration
  • 所以，在定义里的config实际上就是Rails::Engine::Configuration的一个实例
def inherited(base)
  unless base.abstract_railtie?
    Rails::Railtie::Configuration.eager_load_namespaces << base

    base.called_from = begin
      # Remove the line number from backtraces making sure we don't leave anything behind
      call_stack = caller.map { |p| p.sub(/:\d+.*/, '') }
      File.dirname(call_stack.detect { |p| p !~ %r[railties[\w.-]*/lib/rails|rack[\w.-]*/lib/rack] })
    end
  end

  super # go to codes below
end

def inherited(base)
  unless base.abstract_railtie?
    base.send(:include, Railtie::Configurable)
    subclasses << base
  end
end
  • 在Engine里加入了一些初始化设置：set_load_path set_autoload_paths add_routing_paths add_locales add_view_paths load_environment_config append_assets_path prepend_helpers_path load_config_initializers engines_blank_point

Rails::Engine::Configuration (class)

继承自Rails::Railtie::Configurable，记录了Engine的middleware，generators，paths，eager_load_paths，autoload_once_paths，autoload_paths

Rails::Paths (module)

包含两个类：Rails::Paths::Root和Rails::Paths::Path，主要用于记录配置Rails程序的目录信息

Rails::Paths::Root记录了根目录信息，Rails::Paths::Path记录了其他目录信息

允许添加额外的路径配置

Rails::Application (class)

Rails::Application is a Rails::Engine

class << self
  def inherited(base)
    raise "You cannot have more than one Rails::Application" if Rails.application
    super
    Rails.application = base.instance
    Rails.application.add_lib_to_load_path!
    ActiveSupport.run_load_hooks(:before_configuration, base.instance)
  end
end

运用上面的代码，在Rails::Application被继承的时候，就自动初始化了一个实例，并将这个实例赋值给了Rails.application

initialize!方法初始化所有的initializers，对Rails App进行初始化

Rails::Application::Bootstrap (module)

顾名思义，该模块主要用于加载Rails程序初始化的一些设置，用Initializable来完成

初始化过程：load_environment_hook load_active_support set_eager_load initialize_logger initialize_cache initialize_dependency_mechanism bootstrap_hook

Rails::Application::Configuration (class)

用于保存Rails工程的一些设置，包括基本设置，assets设置，路径设置，数据库设置，日志设置，session保存设置等

Rails::Application::Finisher (module)

用于最后加入一些初始化设置，用Initializable来完成

Rails::Application::RoutesReloader (class)

用于动态加载Rails程序的路由设置，用ActiveSupport::FileUpdateChecker来完成对文件修改的侦测

Rails::Initializable (module)

包含了Rails::Initializable::Initializer和Rails::Initializable::Collection，用于存储所有初始化过程 Rails::Initializable::Collection里面运用拓扑排序，把所有的初始化依赖关系进行了有序排列，然后逐一加载

常用到的方法：Rails::Initializable.initializer

def initializer(name, opts = {}, &blk)
  raise ArgumentError, "A block must be passed when defining an initializer" unless blk
  opts[:after] ||= initializers.last.name unless initializers.empty? || initializers.find { |i| i.name == opts[:before] }
  initializers << Initializer.new(name, nil, opts, &blk)
end

使用方法

class MyRailtie < Rails::Railtie
  initializer "my_railtie.configure_rails_initialization" do
    # some initialization behavior
  end
  
  initializer "my_railtie.configure_rails_initialization" do |app|
    app.middleware.use MyRailtie::Middlewarend
  end
end

Rails::Generators (module)

包含了Base，Actions，ActiveModel，AppBase，Migration，NamedBase，ResourceHelpers，TestCase等等

Rails的生成器是基于Thor来实现的

Rails::Info (class)

记录加载的Ruby、Rails相关版本信息，ActiveSupport,ActiveRecord,ActionPack,ActionMailer等相关版本信息，Rack Middleware加载情况，以及App根目录，运行环境和数据库相关信息。

Rails::InfoController (class)

提供Rails相关信息页面渲染。

Rails::WelcomeController (class)

提供新建Rails工程默认首页渲染。