From: "Tom V." <ruby-talk@...>
Date: 2007-05-06T21:46:04+09:00
Subject: Re: dynamically named variables or Constants

Hi Stefano,

thanks for your advice.
However, when I try to call "self.const_get"
from another method (but same class), I get an error:

--> NameError (uninitialized constant MyClass::TOM_VAR)

Here is how I created 'TOM_VAR' (simplified):

def xyz_method

    constant_name = "#{@user.name.upcase}_VAR"
    logger.info("#{constant_name}")
    # output: TOM_VAR

    constant = MyClass.const_set(constant_name, "/path/to/nirvana")
    logger.info("#{constant}")
    # output: /path/to/nirvana

    session[:constant_name] = constant_name

end

In the following method I get the error:

def abc_method

    @constant = MyClass.const_get(session[:constant_name])
    # ERROR

end

Thanks for helping me out
Tom.


On Sun, 6 May 2007 20:21:53 +0900
Stefano Crocco <stefano.crocco@alice.it> wrote:

> Alle domenica 6 maggio 2007, Tom V. ha scritto:
> > Hi,
> >
> > for each user I need to create and call
> > a dynamically named _GLOBAL_ variable (or Constant)
> > labeled with the user name.
> > To make it clear what I mean:
> >
> > # begin "Ruby Pseudocode"
> >    user_name = "tom"
> >    $#{user_name}_dyn_var = "/path/to/nirvana"
> > # end "Ruby Pseudocode"
> >
> > Is there a way to do that?
> > How would I call that new variable '$#{user_name}_dyn_var' ?
> > I tried "Module::const_set":
> >
> > # begin Ruby
> >    constant_name = "#{user_name.upcase}_VAR"
> >    constant = self::class::const_set(constant_name, "/path/to/nirvana")
> > # end Ruby
> >
> > but couldn't find a way to call "#{user_name.upcase}_VAR".
> >
> > you may ask why I either need a global var or a Constant:
> > I am using the "live_tree" plugin
> > from http://www.epiphyte.ca/code/live_tree.html
> > to create a file system browser.
> > As far as I can tell,
> > the plugin requires either a global var or a Constant
> > to initialize the file system model.
> >
> > If someone has tried this plugin before
> > and found another solution, let me know.
> > The author is not responding to my mails.
> >
> > Thanks for your input,
> > Tom.
> 
> I'm not sure about what you mean when saying 'a way to 
> call "#{user_name.upcase}_VAR". If you mean how to get the value of the 
> constant, then you can use const_get, which works like const_set:
> 
> self.class.const_get( constant_name)
> => "/path/to/nirvana"
> 
> I hope this helps
> 
> Stefano
>