From: J2M <james2mccarthy@...>
Date: 2006-12-12T23:59:28+09:00
Subject: Re: How do I catch a missing method on a passed block?


dblack@wobblini.net wrote:

> Hi --
>

> > class Foo
> >    def bar(quantal, *args, &block)
> >      if block_given?
> >        lambd = lambda(&block)
> >        class << lambd
> >          @@return = {}.extend(Appenders::Hashs)
> >          def method_missing(m, *args, &block)
> >            return @@return << { m.to_sym => args_to_attributes(args) }
>
> I'm curious where args_to_attributes is defined.  Is it a top-level
> method?

I just include it into the singleton class, I just chopped it out here!

>
> >          end
> >        end
> >        attributes = lambd.instance_eval(&lambd)
> >      end
> >      parse quantal, attributes
>
> If that if block hasn't run, attributes is going to be undefined.  Did
> you mean to put this line inside the block?

If no block is passed, I had some code (that is snipped for the sake of
brevity) to build the attributes.

Sorry lazy cut and paste job, I should have stripped it back to the
original question.

>
> >    end
> > end # Foo
> >
> > What made this sweet for me was turning the &block into a lambda let me
> > return the result from the instance_eval to bar where other solutions
> > kept them in scope of the &block.
>
> But the block *is* a lambda :-)  That's what the &block argument does:
> it captures the code block in an object and assigns a variable to it.

But without the lambda it is a raw proc that doesn't return the result
of the method - from what I understand from page 344 of Pickaxe. I
tried without and didn't get the result passed back from
method_missing, but I will now test that again :-)

> You could probably also get rid of the class variable by using
> define_method.  (Not essential, but always a bit of a plus style-wise,
> I think.)

Sweet, didn't think of that, I was wanting to get rid of it.

Thanks David.