class.class = class

[Rubynewbie Rubynewbie]

I understand that when you define a new class it´s an instance of
Class...

class Test
end

So you can treat "Test" as an object and asks its class :

Test.class

Class


Is this Class itself an object ?

Because when i do Class.class, ruby gives me 'Class'

So is Class an instance of itself? I don´t understand the logic behind
this

Thanks

 

[Bertram Scharpf]

Hi,

Am Freitag, 17. Jul 2009, 20:54:26 +0900 schrieb Rubynewbie Rubynewbie:

I understand that when you define a new class it=C2=B4s an instance of
Class...
=20
class Test
end
=20
So you can treat "Test" as an object and asks its class :
=20
Test.class
=20
Class
=20
=20
Is this Class itself an object ?

Yes, it is:

Test.class.ancestors
# =3D> [Class, Module, Object, Kernel]
Class.class
# =3D> Class
Class.class.ancestors
# =3D> [Class, Module, Object, Kernel]

Bertram


--=20
Bertram Scharpf
Stuttgart, Deutschland/Germany
http://www.bertram-scharpf.de

 

[James Coglan]

So is Class an instance of itself? I don=B4t understand the logic behind

this

Well then you'll love this:

Class.class
#=3D> Class

Class.superclass
#=3D> Module

Class.superclass.superclass
#=3D> Object

Module.class
#=3D> Class

Object.class
#=3D> Class

Object.ancestors
#=3D> [Object, Kernel]

Kernel.class
#=3D> Module

So Object and Module are instances of a subclass of themselves, and Object
inherits from Kernel, which is a Module, a subclass of Object. Fun!

The way this actually works is that a Ruby interpreter will implement Objec=
t
using low-level building blocks, then implement Module and Class on top of
that, then perform a bunch of voodoo to make Object and Module *look* like
first-class Class instances.

Some quick rules on Ruby's type system that I find helpful:

* Object is the base type. Everything is an Object.

* Module is a type of Object that stores Methods. A module contains a list
of methods, and possibly pointers to one or more 'parent' modules mixed in
using `include`.

* Class is a type of Module that not only stores Methods but can also spawn
new Objects that have the class's methods. Additionally, classes have extra
inheritance semantics in that subclassing is more restrictive than mixins,
and class methods are inherited when subclassing.

* Kernel is an *instance* of Module that stores the core methods common to
all Objects. It is mixed into Object after Module is created, thereby addin=
g
the core methods to all extant objects in the Ruby runtime.

 

[Rubynewbie 72]

Thanks for the responses...

I´m starting to see the light at the end of the tunnel...

Still...I need to do more experimentation with the language because i
still have that "which came first, the chicken or the egg?" feeling

 

[Eleanor McHugh]

Thanks for the responses...

I=B4m starting to see the light at the end of the tunnel...

Still...I need to do more experimentation with the language because i
still have that "which came first, the chicken or the egg?" feeling

A: the omelette


Ellie

Eleanor McHugh
Games With Brains
http://slides.games-with-brains.net

 

[Eric Hodel]

Thanks for the responses...

I=B4m starting to see the light at the end of the tunnel...

Still...I need to do more experimentation with the language because i
still have that "which came first, the chicken or the egg?" feeling

Object comes first from (object.c):

rb_cObject =3D boot_defclass("Object", 0);
rb_cModule =3D boot_defclass("Module", rb_cObject);
rb_cClass =3D boot_defclass("Class", rb_cModule);

In 1.9, it's BasicObject that comes first.=