From: "Shot (Piotr Szotkowski)" <shot@...>
Date: 2009-11-15T01:22:13+09:00
Subject: Re: Surprising behavior when extending instances

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Jim Crossley:

> This surprised me:

>   module English; def say; "yes"; end; end
>   module French; def say; "oui"; end; end
>   x =3D Object.new
>   x.extend English

This adds English to the front of the method look-up path.

>   x.say                 # "yes"

At this point, the #say method is first looked-up in English.

>   x.extend French

This adds French to the front of the method look-up path.

>   x.say                 # "oui"

At this point, the #say method is first looked-up in French.

>   x.extend English

Hey, English is already in the method look-up path, no need to add it!

>   x.say                 # "oui"

Oui, French is still at the front of the method look-up path=E2=80=A6

> What wrong assumptions am I making that this surprises me?

That the second #extend call moved English
to the front of the method look-up path.

> What is the more elegant "Ruby way" of
> alternating an object's behavior at runtime?

I don=E2=80=99t have hand-on experience, and there probably is a simple,
canonical way, but I=E2=80=99d start with looking at Object#instance_eval.

=E2=80=94 Shot
--=20
Anyone who finds the MS Office ribbon intuitive is
not a member of the human species as I understand it.
                                     [William Morgan]

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