From: Josh Cheek <josh.cheek@...>
Date: 2010-02-08T16:11:03+09:00
Subject: Re: confused about the superclass

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On Sun, Feb 7, 2010 at 9:13 PM, Ruby Newbee <rubynewbee@gmail.com> wrote:

> Hello,
>
> Please see the code about, why Myclass.superclass is "Object"? But I
> think it should be "Module".
>
> Thanks for your helps.
>
>
class MyClass
end

MyClass.class       # => Class
MyClass.superclass  # => Object
MyClass.ancestors   # => [MyClass, Object, Kernel]

Class.class         # => Class
Class.superclass    # => Module
Class.ancestors     # => [Class, Module, Object, Kernel]

From here, I see that MyClass's class and superclass are congruent with it's
ancestors, and so are Class's. However, I am also a bit confused, it seems
that if MyClass inherits from Class, then it should include Module in it's
ancestors. I thought about it a bit, and decided to check if included
modules of Class are visible to MyClass

----------

module DoYouSeeMe
end

class Class
  include DoYouSeeMe
end

MyClass.class       # => Class
MyClass.superclass  # => Object
MyClass.ancestors   # => [MyClass, Object, Kernel]

Class.class         # => Class
Class.superclass    # => Module
Class.ancestors     # => [Class, DoYouSeeMe, Module, Object, Kernel]

So apparently not. I decided to generalize this into a hypothesis that
included modules are not visible to subclasses.

----------

class MyClass
  include DoYouSeeMe
end
class MyInheritedClass < MyClass
end

MyClass.class                   # => Class
MyClass.superclass              # => Object
MyClass.ancestors               # => [MyClass, DoYouSeeMe, Object, Kernel]

MyInheritedClass.class          # => Class
MyInheritedClass.superclass     # => MyClass
MyInheritedClass.ancestors      # => [MyInheritedClass, MyClass, DoYouSeeMe,
Object, Kernel]

----------

class MyClass
  include DoYouSeeMe
end
class MySubClass < MyClass
end

MyClass.class                   # => Class
MyClass.superclass              # => Object
MyClass.ancestors               # => [MyClass, DoYouSeeMe, Object, Kernel]

MySubClass.class                # => Class
MySubClass.superclass           # => MyClass
MySubClass.ancestors            # => [MySubClass, MyClass, DoYouSeeMe,
Object, Kernel]

Apparently I was wrong. I thought about it a little bit more, and decided
that maybe MyClass didn't inherit from Class, but was rather an instance of
class

----------

MyClass.instance_of? Class      # => true
MySubClass.instance_of? MyClass # => false
MyOtherClass = Class.new
MyOtherClass.ancestors          # => [MyOtherClass, Object, Kernel]

This seems to be congruent :)
So, my conclusion is that class and superclass behave correctly, in that
they reflect their ancestry. And the reason MyClass' ancestry is not a
superset of Class' ancestry is because MyClass is not a subclass of Class,
but rather an instance of it. ( I tried making a subclass of Class also, but
got a TypeError )



Hope that helps, thanks for asking, it was a useful exercise :)

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