From: ptkwt@...1.aracnet.com (Phil Tomson)
Date: 2002-01-08T08:59:15+09:00
Subject: Re: Globals and passed objects (fixed)

Nevermind....  I discovered that in one of the classes I do:
#Tool.rb:
class Tool
  @@results_dir = $RESULTS_DIR
....
end

and in the main client program I was defining $RESULTS_DIR _AFTER_
doing a require of Tool:
#client:
require 'Tool'
....
$RESULTS_DIR = "/home/blah/results"

so of course @@results_dir in class Tool was undefined (nil).

Phil


In article <vLp_7.147802$lV4.25469717@e420r-atl1.usenetserver.com>,
Phil Tomson <ptkwt@shell1.aracnet.com> wrote:
>This is related to an application of the Ruby Distributor.
>
>I'm distributing TestCase objects which have a 'run' method to clients.  
>On the clientside there is one global, $RESULTS_DIR, which is the path to 
>a directory where results are stored.  Now, the server (Distributor) 
>instantiates a TestCase object which is then sent to a dRuby object on the 
>Client machine.  The Client then invokes the TestCase objects 'run' 
>method which in turn creates several other objects on the client side.  
>One of the objects relies on $RESULTS_DIR to figure out where to store 
>it's results.  But, $RESULTS_DIR in this context is nil even though we're 
>running on the client and the client program initially set up 
>$RESULTS_DIR.
>
>My theory is that as soon as we run the TestCase object's 'run' method on 
>the client that now TestCase doesn't know anything about the client's 
>globals since the TestCase object was created on the server machine.  Does 
>this make sense?
>
>Here's some very chopped down code that I hope illustrates the problem:
>
>Server side:
>
>tc = TestCase.new()
>distributor.send(tc) #this sends the testcase to the client machine
>
>
>Client side:
>$RESULTS_DIR="/home/results_dir"
>...
>#after receiveing the testcase, tc:
>tc.run 
>#later, now somewhere in tc's run method:
>    File.copy(results, $RESULTS_DIR)
>    #but the copy doesn't succeed because $RESULTS_DIR is nil here
>
>
>
>Why wouldn't $RESULTS_DIR be visible in the context of the tc object's run 
>method?  
>
>Phil
>