#<Class:Foo>
是给定类 Foo
的特殊/匿名类。如果该特殊/匿名类也被扩展了,那么另一个特殊类就会被创建 - 因此表示为 #<Class:#<Class:Foo>>
。
特殊类的父类是 Object
类的特殊类,其父类是 BasicObject
的特殊类。同样,另一个特殊类的特殊类的父类是 Object
类的特殊类,以此类推。
下面的代码与这个解释结合起来可以更深入地理解
p Foo.class
p Foo.class.ancestors
puts "-----------------"
p Foo.singleton_class
p Foo.singleton_class.ancestors
puts "-----------------"
p Foo.singleton_class.singleton_class
p Foo.singleton_class.singleton_class.ancestors
它的输出为
Class
[Class, Module, Object, Kernel, BasicObject]
-----------------
#<Class:Foo>
[#<Class:Foo>, #<Class:Object>, #<Class:BasicObject>, Class, Module, Object, Kernel, BasicObject]
-----------------
#<Class:#<Class:Foo>>
[#<Class:#<Class:Foo>>, #<Class:#<Class:Object>>, #<Class:#<Class:BasicObject>>, #<Class:Class>, #<Class:Module>, #<Class:Object>, #<Class:BasicObject>, Class, Module, Object, Kernel, BasicObject]
以上所见的Eigen类层次结构可以重复到任意级别。例如:
p Foo.singleton_class.singleton_class.singleton_class.singleton_class.singleton_class
puts "-----------------"
p Foo.singleton_class.singleton_class.singleton_class.singleton_class.singleton_class.ancestors
上面的代码输出
#<Class:#<Class:#<Class:#<Class:#<Class:Foo>>>>>
-----------------
[#<Class:#<Class:#<Class:#<Class:#<Class:Foo>>>>>, #<Class:#<Class:#<Class:#<Class:#<Class:Object>>>>>, #<Class:#<Class:#<Class:#<Class:#<Class:BasicObject>>>>>, #<Class:#<Class:#<Class:#<Class:Class>>>>, #<Class:#<Class:#<Class:#<Class:Module>>>>, #<Class:#<Class:#<Class:#<Class:Object>>>>, #<Class:#<Class:#<Class:#<Class:BasicObject>>>>, #<Class:#<Class:#<Class:Class>>>, #<Class:#<Class:#<Class:Module>>>, #<Class:#<Class:#<Class:Object>>>, #<Class:#<Class:#<Class:BasicObject>>>, #<Class:#<Class:Class>>, #<Class:#<Class:Module>>, #<Class:#<Class:Object>>, #<Class:#<Class:BasicObject>>, #<Class:Class>, #<Class:Module>, #<Class:Object>, #<Class:BasicObject>, Class, Module, Object, Kernel, BasicObject]