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comp.lang.ruby

strange bit of code

Matthew Johnson

8/16/2006 3:59:00 AM

I came across an unusual behavior of remove_method the other day.
When I discovered that it didn't work as I expected I experimented
until I found a relatively simple example illustrating what happens.
The show method doesn't seem to be removed when the example calls
remove_method, but it is removed as soon as a show method is defined
in any module or class, even if is defined in a module or class not
related in any way to the module it is removed from. Can anyone
explain why this works the way it does?

Thanks,
Matthew

module A
module B
def show
"pr"
end
end
end
class C
include A::B
end

p "normal: " << C.new.show

p C.instance_methods - C.superclass.instance_methods
p A::B.instance_methods
module A
module B
remove_method :show
end
end
p C.instance_methods - C.superclass.instance_methods
p A::B.instance_methods

p "shouldn't work - pr was removed " << C.new.show

module A
end

p "still shouldn't work " << C.new.show

module S
def show
end
end
# the next line throws an error
p "defining a show method in any class or module now causes it to
stop working " << C.new.show
2 Answers

Nobuyoshi Nakada

8/16/2006 6:24:00 AM

0

Hi,

At Wed, 16 Aug 2006 12:58:57 +0900,
Matthew Johnson wrote in [ruby-talk:208741]:
> I came across an unusual behavior of remove_method the other day.
> When I discovered that it didn't work as I expected I experimented
> until I found a relatively simple example illustrating what happens.
> The show method doesn't seem to be removed when the example calls
> remove_method, but it is removed as soon as a show method is defined
> in any module or class, even if is defined in a module or class not
> related in any way to the module it is removed from. Can anyone
> explain why this works the way it does?

I think it's a fixed bug. Can you try it with latest snapshot?

$ grep -C2 rb_clear_cache ChangeLog
Mon Jul 10 09:29:12 2006 Nobuyoshi Nakada <nobu@ruby-lang.org>

* eval.c (rb_clear_cache_for_undef): clear entries for included
module. fixed: [ruby-core:08180]

--
Nobu Nakada

Matthew Johnson

8/16/2006 10:49:00 AM

0

> I think it's a fixed bug. Can you try it with latest snapshot?
>
> $ grep -C2 rb_clear_cache ChangeLog
> Mon Jul 10 09:29:12 2006 Nobuyoshi Nakada <nobu@ruby-lang.org>
>
> * eval.c (rb_clear_cache_for_undef): clear entries for included
> module. fixed: [ruby-core:08180]
>
> --
> Nobu Nakada


Thanks! That does look like the source of it. It makes much more
sense now... :)

Matthew