From: pharrington <xenogenesis@...>
Date: 2010-01-13T05:05:07+09:00
Subject: Re: instance_eval with local variable

On Jan 12, 2:57 pm, Phrogz <phr...@mac.com> wrote:
> On Jan 12, 12:23 pm, Phrogz <phr...@mac.com> wrote:
> [snip]> For those interested in second-guessing my approach and coming up with
> > a better way to achieve the same end goal
>
> FWIW, there is a workaround I've come up with. Instead of trying to
> evaluate the proc in the scope and access instance variables directly,
> I can pass the object to the proc and work from its public interface.
> My original code is thus changed:
>
> > def self.process_snippets( html )
> >   @snippets.inject(html){ |h,(regexp,handler)| h.gsub( regexp, &handler ) }
>
> def self.process_snippets( html, bundle )
>   @snippets.inject(html){ |h,(r,proc)| h.gsub(r){ |s| proc
> [s,bundle] } }
>
> >   # Mark $$foo$$ as glossary items.
> >   DocuBot.handle_snippet /\$\$\w[^$]+\$\$/ do |match|
> >     # TODO: look up the glossary term in the bundle's glossary
> >     # and insert appropriate text, or flag a new glossary term
> >     "<span class='glossary'>#{match[2..-3]}</span>"
> >   end
>
> DocuBot.handle_snippet /\$\$\w[^$]+\$\$/ do |match, bundle|
>   term = match[2..-3]
>   defn = bundle.glossary[term]
>   "<span class='glossary' title='#{defn}'>#{term}</span>"
> end
>
> I'm thus unblocked in my endeavors, but still interested in the
> metaprogramming needed to accomplish my original goal. I was actually
> a little surprised that instance_eval doesn't take an arbitrary number
> of arguments in the block form and splat them along to the block's
> parameters.

Well, I'm not sure if this is the particular sort of nastiness you're
looking for, but.... defining a new method with the proc works..

xeno@amrita:~/projects  $ cat nasty.rb
obj = Object.new
obj.instance_variable_set :@who, "foo"
@who = "main"
holla = lambda {|str| p @who, str}

class << obj
  def eigen
    class << self; self; end
  end
end

obj.eigen.send(:define_method, :holla, &holla)
obj.holla "horrah"
xeno@amrita:~/projects  $ ruby nasty.rb
"foo"
"horrah"