Module/Object/Class 在Active Support中被重新定义？

最近打算研究rails代码，这样可以更好的学习ruby，发现入手还是比较困难的，rails对ruby运用灵活，加之ruby本身语法的灵活性，很难适应。在Active Support的dependencies.rb中发现了Module/Class/Object的重新定义：

class Module #:nodoc:
  # Rename the original handler so we can chain it to the new one
  alias :rails_original_const_missing :const_missing
  
  # Use const_missing to autoload associations so we don't have to
  # require_association when using single-table inheritance.
  def const_missing(class_id)
    Dependencies.load_missing_constant self, class_id
  end
  
  def unloadable(const_desc = self)
    super(const_desc)
  end
  
end

class Class
  def const_missing(class_id)
    if [Object, Kernel].include?(self) || parent == self
      super
    else
      begin
        begin
          Dependencies.load_missing_constant self, class_id
        rescue NameError
          parent.send :const_missing, class_id
        end
      rescue NameError => e
        # Make sure that the name we are missing is the one that caused the error
        parent_qualified_name = Dependencies.qualified_name_for parent, class_id
        raise unless e.missing_name? parent_qualified_name
        qualified_name = Dependencies.qualified_name_for self, class_id
        raise NameError.new("uninitialized constant #{qualified_name}").copy_blame!(e)
      end
    end
  end
end

class Object #:nodoc:
  
  alias_method :load_without_new_constant_marking, :load
  
  def load(file, *extras)
    Dependencies.new_constants_in(Object) { super(file, *extras) }
  rescue Exception => exception  # errors from loading file
    exception.blame_file! file
    raise
  end

  def require(file, *extras)
    Dependencies.new_constants_in(Object) { super(file, *extras) }
  rescue Exception => exception  # errors from required file
    exception.blame_file! file
    raise
  end

  # Mark the given constant as unloadable. Unloadable constants are removed each
  # time dependencies are cleared.
  # 
  # Note that marking a constant for unloading need only be done once. Setup
  # or init scripts may list each unloadable constant that may need unloading;
  # each constant will be removed for every subsequent clear, as opposed to for
  # the first clear.
  # 
  # The provided constant descriptor may be a (non-anonymous) module or class,
  # or a qualified constant name as a string or symbol.
  # 
  # Returns true if the constant was not previously marked for unloading, false
  # otherwise.
  def unloadable(const_desc)
    Dependencies.mark_for_unload const_desc
  end

end

首先，这些关键字可以被重新定义吗？
其次，在dependencies.rb中如是定义之后，是否在actioncontroller,actionview,actionrecord中这些关键字的引用就采纳了新的定义？
版上有没有研读过rails代码的对这个问题如何看待呢？

明白了，是我概念又混淆了，ruby对于class/module的定义不是封闭的，它们可以随时补充新的定义。