From: Gary Wright <gwtmp01@...>
Date: 2007-11-08T04:15:52+09:00
Subject: Re: instance_eval to evaluate methods inside a block in cont


On Nov 7, 2007, at 3:58 AM, Adam Anderson wrote:
> From what I am reading it would seem that this is just not a
> possibility, however.

You could use method_missing in the implicit object to delegate
the message to another object:

class A
   def foo
     warn "foo in #{self.inspect}"
   end
   def backup=(b); @backup = b; end
   def method_missing(*args, &block)
     if @backup
       @backup.send(*args, &block)
     else
       super
     end
   end
end


class B
   def bar
     warn "bar in #{self.inspect}"
   end
   def with(x, &b)
     x.backup = self
     x.instance_eval &b
   end
end

a = A.new
b = B.new.with(a) {
       foo            # foo in instance of A
       bar            # bar in instance of B
}