From: Robert Klemme <bob.news@...>
Date: 2004-12-15T19:37:16+09:00
Subject: Re: Mixin questions


"Johan Nilsson" <johan.nilsson@---.esrange.ssc.se> schrieb im Newsbeitrag
news:1103100242.441c484f346652f8ca3ea31133c45618@teranews...
>
> "Robert Klemme" <bob.news@gmx.net> wrote in message
> news:328e5nF3jvaf9U1@individual.net...
> >
> > "Johan Nilsson" <johan.nilsson@---.esrange.ssc.se> schrieb im
Newsbeitrag
> > news:1103032112.3aa9129fd718fc17e4d9eb2e027a3e52@teranews...
> > >
> > > "Robert Klemme" <bob.news@gmx.net> wrote in message
> > > news:3286taF3it29pU1@individual.net...
> > > >
> > >
>
> [snip]
>
> > >
> > > I still don't see how the mixin can get to the protected methods
> > though - I
> > > get "NoMethodError: protected method 'my_stuff' called for ..." if I
try
> > > somehing like my original code.
> >
> > I haven't a solution for this yet.  I tried with instance_eval but to
no
> > avail.  Maybe send works.  Did you try that?
>
> No, and it actually works. What's the difference? I'm just starting to
use
> Ruby for real.

#send bypasses a lot of things - that's why, I guess.

> > > > > In english, I want to create an instance of Foo from within the
> > mixin's
> > > > > supplied class method. The first question still applies though.
> > > >
> > > > You mean like this?
> > > >
> > > > module Mix
> > > >   def test_it
> > > >     p self::FOO
> > > >   end
> > > > end
> > > >
> > > > class Test
> > > >   extend Mix
> > > >   FOO = "bar"
> > > > end
> > >
> > > Yes, but in my (unfortunately) more complex case I get "dynamic
constant
> > > assignment" whenever I add "self::<constant>" to the mixin (reported
> > from
> > > the point where the class constant is defined).
> >
> > But then you're assigning the constant more than once.  From your
example
> > I though you just wanted to access (= read) it.  Which Ruby version
are
> > you using?
>
> Sorry for being unclear, but I'm not assigning more than once (at least
I'm
> not trying to). I'm trying to use either self::<constant> or
> self.class.const_get(:<constant>) as rvalues, and the former does not
work
> in the Mixin. Oh, yes, and it is within a define_method scope - could
that
> matter, e.g.:

I think it does.  self at the time of execution is an instance and not the
class object at hand.

>     def ...
>         define_method(:initialize) { ||
>             ...
>             @x = self::<constant> # dynamic constant assignment
>             ...
>         }
>     end

So here are two alternatives:

    def ...
        define_method(:initialize) { ||
            ...
            @x = self.class::<constant> # dynamic constant assignment
            ...
        }
    end


    def ...
        me = self
        define_method(:initialize) { ||
            ...
            @x = me::<constant> # dynamic constant assignment
            ...
        }
    end


> Platform is Ruby 1.8.2.rc9 on WinXP.
>
> [...some minute later...] Oh, but wait - self refers to the object here.
> Trying to use self.class::ID works! Sorry for the noise.
>
> >
> > > Using
> > > ...self.class.const_get("<constant>") works fine though in the
mixin.
> >
> > Strange.
> >
> > > The code is a bit too much to post though, if I can reduce it I'll
try
> > and
> > > post the actual failing code instead.
> >
> > Yeah, it would be good to see the real source of the problem.  At the
> > moment I feel a bit tapping in the dark. :-)
>
> That might not be necessary any more, thanks!

You're welcome.  I'm glad I could help.

Kind regards

    robert