From: Ronald Fischer <ronald.fischer@...>
Date: 2007-08-29T22:15:47+09:00
Subject: Re: Looking for help implementing static variables

> I am working on an application where we are trying to 
> remember previous
> values from an execution of a Ruby program. Basically, we 
> have a screen
> where a user can type an 'X' into either a 'Yes' or a 'No' 
> box. We do not
> want them to type Xs into both boxes. So if the 'Yes' box has 
> an X in it,
> and then the user types an 'X' into the 'No' box, we want to 
> clear the 'Yes'
> box automatically. Our Ruby program runs each time the user 
> tabs out of a
> field on the screen or presses the Enter key.
>  
> Apparantly, Ruby does not have static variables where I can 
> store the box
> values and refer to them when the program runs again

Don't know whether this is the best solution, but I usually
marshal them to a file when the program is shut down, and reread
it when it is started up again. For example (using global variables),
to save the value of $checkstate for next execution, I write

   require 'pp'
   ...
   File.write("config.rc","w") { |fh|
     fh.puts('$checkstate='+$checkstate.pretty_inspect) }

and read it back with

   eval(File.read("config.rc")) # sets $checkstate to the saved value

If you are unhappy with the idea of using global variables, you can
do it like this:

   ...
   File.write("config.rc","w") { |fh|
     fh.puts('CHECKSTATE='+checkstate.pretty_inspect) }

(note the usage of upper case to denote a constant) and read it back
like
this:

   eval("module RC\n"+File.read("config.rc")+"\nend")
   checkstate=RC::CHECKSTATE # sets checkstate to the saved value

Another possibility, suggested already in the list - but one which 
I have not used myself yet (though I would like to try it out on 
the next occasion) - is to use the Marshal module. See

http://www.ruby-doc.org/core/classes/Marshal.html

Ronald