[ruby-talk:00550] Re: Question concerning modules (1)

Hi,

From: [e-mail]
Subject: [ruby-talk:00546] Question concerning modules (1)
Date: Tue, 3 Aug 1999 12:49:27 +0200 (MET DST)

> rbc0> foo = Foo.clone
> Foo
> 
> # Now I have cloned `Foo' and store it into a variable
> 
> rbc0> foo.show
> NameError: (eval):1: undefined method `show' for Foo:Module
> 
> # Hmm, the instance in `foo' doesn't know `show' yet. Is okay, I guess.
> # Same reason as before.

`show' is foo's instance_method, not method.

> rbc0> Foo.instance_variables.include? "@ivar"
> true
> 
> # Aha! `Foo' contains the instance variable.

Yes. But it's not instance variable of Foo's instance.

> rbc0> foo.instance_variables.include? "@ivar"
> true
> 
> # And so does `foo'!
> 
> rbc0> Foo.methods.include? :show
> false
> 
> # Oops! `Foo' knows about instance variables, but not methods????

Object#methods returns string array. You have to write `include? "show"'.

> rbc0> foo.methods.include? :show
> false
> 
> # Same here...
> 
> rbc0> foo.extend(Foo)
> Foo
> 
> # Now the instance referred by `foo' will be extend by module `Foo'. I
> # would not assume something special here! As `foo' is already a `Foo',
> # it should not change anything, should it?

No. Just foo's class (singleton class?) achive the Foo's feature.

> rbc0> foo.methods.include? :show
> false
> 
> # Right! It has changed nothing. Or ... ?

foo.methods.include? "show" #--> true

> rbc0> foo.show
> Value is: `12'
> nil
> 
> # Hah! Gotcha! What is that? Please help and explain!

Cause foo's (singleton) class is extended by Foo, foo has the method `show'.

Hope this helps,
--
sorry for my broken english
best regards
Kazuhiro HIWADA ([e-mail])