Question

我正在看这个boot.rb文件：

http://github.com/bestbuyremix/BBYIDX/blob/master/config/boot.rb

在试图理解之后，就好像我到目前为止没有学到任何东西。

有人可以详细说明这里发生了什么吗？

我不知道有人怎么能想出这个？

# Don't change this file!
# Configure your app in config/environment.rb and config/environments/*.rb

RAILS_ROOT = "#{File.dirname(__FILE__)}/.." unless defined?(RAILS_ROOT)

module Rails
  class << self
    def boot!
      unless booted?
        preinitialize
        pick_boot.run
      end
    end

    def booted?
      defined? Rails::Initializer
    end

    def pick_boot
      (vendor_rails? ? VendorBoot : GemBoot).new
    end

    def vendor_rails?
      File.exist?("#{RAILS_ROOT}/vendor/rails")
    end

    def preinitialize
      load(preinitializer_path) if File.exist?(preinitializer_path)
    end

    def preinitializer_path
      "#{RAILS_ROOT}/config/preinitializer.rb"
    end
  end

  class Boot
    def run
      load_initializer
      Rails::Initializer.run(:set_load_path)
    end
  end

  class VendorBoot < Boot
    def load_initializer
      require "#{RAILS_ROOT}/vendor/rails/railties/lib/initializer"
      Rails::Initializer.run(:install_gem_spec_stubs)
    end
  end

  class GemBoot < Boot
    def load_initializer
      self.class.load_rubygems
      load_rails_gem
      require 'initializer'
    end

    def load_rails_gem
      if version = self.class.gem_version
        gem 'rails', version
      else
        gem 'rails'
      end
    rescue Gem::LoadError => load_error
      $stderr.puts %(Missing the Rails #{version} gem. Please `gem install -v=#{version} rails`, update your RAILS_GEM_VERSION setting in config/environment.rb for the Rails version you do have installed, or comment out RAILS_GEM_VERSION to use the latest version installed.)
      exit 1
    end

    class << self
      def rubygems_version
        Gem::RubyGemsVersion if defined? Gem::RubyGemsVersion
      end

      def gem_version
        if defined? RAILS_GEM_VERSION
          RAILS_GEM_VERSION
        elsif ENV.include?('RAILS_GEM_VERSION')
          ENV['RAILS_GEM_VERSION']
        else
          parse_gem_version(read_environment_rb)
        end
      end

      def load_rubygems
        require 'rubygems'
        min_version = '1.1.1'
        unless rubygems_version >= min_version
          $stderr.puts %Q(Rails requires RubyGems >= #{min_version} (you have #{rubygems_version}). Please `gem update --system` and try again.)
          exit 1
        end

      rescue LoadError
        $stderr.puts %Q(Rails requires RubyGems >= #{min_version}. Please install RubyGems and try again: http://rubygems.rubyforge.org)
        exit 1
      end

      def parse_gem_version(text)
        $1 if text =~ /^[^#]*RAILS_GEM_VERSION\s*=\s*["']([!~<>=]*\s*[\d.]+)["']/
      end

      private
        def read_environment_rb
          File.read("#{RAILS_ROOT}/config/environment.rb")
        end
    end
  end
end

# All that for this:
Rails.boot!

Answer 1

如果您正在学习Rails，那么就不是这样做的地方。也许您认为为了使用它，您需要了解代码从一开始如何流动？不要那样做。：）

如果您正在学习rails，请使用许多指南和教程中的任何一个来构建基本站点。

至于这段代码，它采用的一些概念涉及ruby的标志性class << self这是对元类的批判性阅读：http://yehudakatz.com/2009/11/15/metaprogramming-in-ruby-its-all-about-the-self/

底部的Rails.boot!会让您得出结论“在对象boot!上调用方法Rails ...返回到顶部，您会看到

module Rails
   class << self
     def boot!
       unless booted?
       preinitialize
       pick_boot.run
     end
   end
 ...

在这里你可以看到class << self背后的魔力......它在模块本身上创建了boot!方法。从那里你可以跟踪整个文件中的方法调用，因为它检查是否存在preinitializer文件......

pick_boot会返回一个对象VendorBoot或GemBoot，具体取决于vendor_rails?的结果，然后调用run方法。

从那里你有一些Boot类的标准类继承，因为它设置了其余的库。希望这能让你开始。：）

这实际上是非常好的OO风格......小方法和类都可以完成一项简单的任务。还有OO继承和几个常见的ruby习语。总而言之，这是一个非常好的红宝石代码。：）

<强>更新

如果以更加程序化的方式编码，这是一个粗略的估计：

RAILS_ROOT = "#{File.dirname(__FILE__)}/.." unless defined?(RAILS_ROOT)

unless defined? Rails::Initializer
  preinitializer_path = "#{RAILS_ROOT}/config/preinitializer.rb"
  load() if File.exist?(preinitializer_path)
  if File.exist?("#{RAILS_ROOT}/vendor/rails")
    require "#{RAILS_ROOT}/vendor/rails/railties/lib/initializer"
    Rails::Initializer.run(:install_gem_spec_stubs)
    Rails::Initializer.run(:set_load_path)
  else
    begin
      require 'rubygems'
      min_version = '1.1.1'
      rubygems_version = Gem::RubyGemsVersion if defined? Gem::RubyGemsVersion
      unless rubygems_version >= min_version
        $stderr.puts %Q(Rails requires RubyGems >= #{min_version} (you have #{rubygems_version}). Please `gem update --system` and try again.)
        exit 1
      end

    rescue LoadError
      $stderr.puts %Q(Rails requires RubyGems >= #{min_version}. Please install RubyGems and try again: http://rubygems.rubyforge.org)
      exit 1
    end
    begin
      if defined? RAILS_GEM_VERSION
         version = RAILS_GEM_VERSION
      elsif ENV.include?('RAILS_GEM_VERSION')
        version =  ENV['RAILS_GEM_VERSION']
      else
         version = $1 if (File.read("#{RAILS_ROOT}/config/environment.rb")) =~ /^[^#]*RAILS_GEM_VERSION\s*=\s*["']([!~=]*\s*[\d.]+)["']/
      end
      if version
        gem 'rails', version
      else
        gem 'rails'
      end
    rescue Gem::LoadError => load_error
      $stderr.puts %(Missing the Rails #{version} gem. Please `gem install -v=#{version} rails`, update your RAILS_GEM_VERSION setting in config/environment.rb for the Rails version you do have installed, or comment out RAILS_GEM_VERSION to use the latest version installed.)
      exit 1
    end
    require 'initializer'
  end
end

Answer 2

这实际上是做了很多花哨的步法来确定rails源代码的位置。

您可以将当前rails gem源代码“冻结”到供应商目录中。如果您可能安装了多个版本的rails并且希望确保您的应用程序仅使用该版本进行开发和运行，则此功能非常有用。

此代码检查是否已将某个版本的rails冻结到供应商目录中，如果是，请使用该目录。如果冻结版本不可用，它会尝试使用本地宝石，但首先要确保它们符合最低版本要求。

有关“冻结”宝石的更多信息，请使用“rake -T”查看可用于项目的rake任务的说明。

学习RoR，有人可以从H ** ll解释这个boot.rb吗？

2 个答案: