From: Tom Cloyd <tomcloyd@...>
Date: 2009-02-11T17:17:22+09:00
Subject: simple class question

Tonight I'm exploring the problem of tossing a value at a class instance 
and getting a value back - having it behave like a method, in other 
words. I've not looked at this before, and I don't have much confidence 
about what I'm doing. I have a simple example from Thomas 3rd ed., and 
have modified it a bit. It's not working as I'd expect - at all.

The code:

=== begin code
# test.rb

def main
  test = Test.new 
  puts 'bye'  # <=========== line 6
end

class Test
 
  def t1=(val)
  @val = val
  return 99
  end

  def t2=(val)
  @val = val * 2
  return 99
  end

end

%w(rubygems ruby-debug).each{ |lib| require lib }

Debugger.start
debugger

main

=== end code

I start this, and the debugger  stops it. I put a break point a line 6, 
and continue.
With execution stopped, I enter at the command line:

(rdb:1) p test.t2 = 2
2

I should have gotten 4. I only ever get back the same number I put in. 
Can someone tell me what the problem is, and what I have to do to get 
test.t2 to do this simple thing I'm asking of it?

My other question: the "return 99" business is from Thomas. He doesn't 
explain it. I've been reading about "return" and I cannot account for 
why it's there. It doesn't seem to do any thing. Can someone explain THAT.

Finally, is this general approach I'm taking the best or usual way to 
send data to a class method and get some output? Until now, I thought I 
had to read an accessor variable to get output back, but I'm thinking 
now that that is probably NOT the best way.

What I'm wanting to do, say, create a file object which gives me more 
data when I call upon it (it'll read a record and do some processing, 
then pass back the results. Normally I'd use a method, but I'm trying to 
become more "classy" in my programming, hence this effort. I'm basically 
still struggling to find a good reason to use a class at all. So far, 
it's proven far too difficult to get something OUT of a class instance. 
I don't see the point of the bother, yet. I'm hoping some enlightenment 
will arrive soon.

As always, much thanks for all contributions!

Tom


-- 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Tom Cloyd, MS MA, LMHC - Private practice Psychotherapist
Bellingham, Washington, U.S.A: (360) 920-1226
<< tc@tomcloyd.com >> (email)
<< TomCloyd.com >> (website) 
<< sleightmind.wordpress.com >> (mental health weblog)
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