[ruby-talk:00568] Re: Question concerning modules (1)

Hi,

In message "[ruby-talk:00565] Re: Question concerning modules (1)"
    on 99/08/06, [e-mail] <[e-mail]> writes:

|But following your explanaition, there are many metaclasses in Ruby.
|There seems to be a metaclass for Module, Class, Object, ...
|denoted by your `()' signs. 

Yes.

All objects which define singleton methods have hidden singleton
class.  For classes, they can be called as metaclasses, for they are
(hidden) class of the class.

|But where does (Foo) comes from? And how can I create the aFoo
|instance? I would have to call a class' `new' method to create a
|instance, but Modules have no `new' method.

Singleton classes are defined automagically, if you define singleton
methods for the objects.

|
|>> >> # Aha! `Foo' contains the instance variable.
|>> >
|>> >Yes. But it's not instance variable of Foo's instance.
|
|And again you are speaking from a instance of Foo. What do you
|mean? How do I create instances of Foo? And why do I call the variable
|an instance variable? If it is an instance variable, it should be only
|accessible via Foo's instance, but not from Foo itself, isn't it?

Remember Foo itself is the object, the instance of the class Module.

|Ahh! By extending a module object, that module becomes a instance of
|the module that extends it, right? That means:
|
|	foo.extend foo
|
|would let foo be an instance of itself, right? And here foo would 
|also become a metaclass for itself?

Not really.  Including and extending make `is-a' relation between the
object and the module, so that `Object#kind_of?' returns true for
these modules.  But metalcass is another story.

                                                        matz.