From: Nita Neou <sophoah@...>
Date: 2010-07-08T00:55:10+09:00
Subject: Re: Problem of share variable in function using thread

On Jul 7, 12:15 am, Jesús Gabriel y Galán <jgabrielyga...@gmail.com>
wrote:
> On Tue, Jul 6, 2010 at 6:00 PM, Nita Neou <soph...@gmail.com> wrote:
> > Hi All
>
> > I got a little problem when using thread function and variable, let's
> > say this code :
>
> > require 'rubygems'
> > require 'watir'
> > require 'thread'
>
> > def testfunc(id)
> >        total = id + 5
> >        puts "id #{id} is #{total}"
> > end
>
> > threads = []
> > numberlist = [1, 2, 3]
> > for id in numberlist
> >        threads << Thread.new {testfunc(id)}
> > end
>
> > threads.each { |aThread|  aThread.join }
>
> > my output is :
> > [sophoah@fedora ]$ ruby test.rb
> > id 3 is 8
> > id 3 is 8
> > id 3 is 8
>
> > The fact is that I would like this output :
> > id 1 is 6
> > id 2 is 7
> > id 3 is 8
>
> > I am suspecting that all variable id, and total are all share among
> > all the thread, is that right ? why ? I thought variable in a block
> > were not share among variable ? How can I fix this problem ?
>
> Blocks in Ruby are closures, this means that inside the block you pass
> to Thread.new, the variable id is the same.
> The Thread class has a way to avoid this, take a look at the constructor:
>
> http://ruby-doc.org/core/classes/Thread.html#M000437
>
> You can pass parameters to #new and it will pass them to the block.
> You can use this technique to use a variable in the block that is
> different for each thread, like this:
>
> def testfunc(id)
>   total = id + 5
>   puts "id #{id} is #{total}"
> end
>
> threads = []
> numberlist = [1, 2, 3]
> for id in numberlist
>  threads << Thread.new(id) {|my_id| testfunc(my_id)}
> end
>
> threads.each { |aThread|  aThread.join }
>
> $ ruby threads.rb
> id 1 is 6
> id 2 is 7
> id 3 is 8
>
> Jesus.

Thanks both of you for your answer.

Regards