From: Tim Becker <a2800276@...>
Date: 2006-05-16T20:35:11+09:00
Subject: Re: learn to program

> My real issue is with the excerpt from the book, which would make new
> programmers think they can do whatever they want to an object inside a
> method and not have it affect anything outside of it.  Clearly that is
> not the case.

The book is trying to make a point which is really important and
central to programming. It's difficult to explain, but once it
"clicks" it seems trivial: the variable and the actual object the
variable points at are completely distinct.

Manipulating the variable doesn't change the object it points to, it
just makes the variable point to a different object:

  a = "Some object"	# `a` now points at "Some object"
  b=a 			# `b` now also point at "Some object"
  a = nil 		# `a` now points at nil, but this doesn't change "Some object"

if you'd do this:

  a = a.upcase

`a` now points at the new Object returns by calling the `upcase`
method, i.e. you've changed the location that `a` points to.

Had you done this:
  a.upcase!

this would have changed the object that `a` is pointing at instead of
changing what the variable points at.
   -tim