From: harryo@... (Harry Ohlsen)
Date: 2002-05-02T23:51:38+09:00
Subject: A scoping issue

I'm trying to write a class that constructs a Tk
dialog and am hitting an issue to do with the scope
of instance variables.

As part of the processing, what I want is something
similar to the following code (I've made it non-Tk,
to show up the essence of the problem) ...

class A
   def initialize(&block)
      @code = block
   end
end

class B
   def initialize
      @x = 123

      a = A.new(proc { puts @x })
      a.execute
   end
end

The problem is that, of course, the reference to @x
assumes it's an instance variable of class A, rather
than the one from class B, in the outer scope.

Is there some way I can get the block passed to the
A.new to end up with the @x from the instance of B
that I'm constructing?

Please note that I didn't write the equivalent of
class A (it's a Tk provided one), so I can't cleanly
add an extra variable to its initialize().

Currently, I'm setting a global variable, but I really
dislike that, even though it works OK in this case,
because there'll only ever be one instance of B in
existence at a time.

Is there a clean way I can do this?