From: dblack@...
Date: 2006-09-10T23:19:48+09:00
Subject: Re: patching strings together to make a variable

Hi --

On Sun, 10 Sep 2006, Sy Ali wrote:

> I'm curious to know if I can patch multiple things together to make a 
> variable.
>
> I have some imaginary code snippets.  The most direct way I can think
> of is something like this:
>
> $a = true
> $var = "fail"
> $variable = "pass"
>
> puts "#{$var(if $a == true then "iable" end)}"
>
> since $a == true, I would like this to become:
> puts "#{$variable}"
>
> But this doesn't work.  I didn't expect it to, but is something like
> this possible?  Am I stuck with this? :
>
> puts "#{if $a == true then $variable else $var end}"
>
>
> What I'd really like to learn is how I can patch multiple strings
> together and call it a variable.  I think I'm just missing some simple
> piece of this puzzle..
>
> The imaginary code would be:
>
> ab = "pass"
> puts ("a" + "b").to_variable
>
> Or to a global, an instance variable, etc.. envisioned like this:
>
> puts $("a" + "b")
> puts @("a" + "b")
>
>
> If there's a simple way to do this, a code snippet or a pointer to a
> manual reference would be all I need.

http://www.perl.org :-)  Perl has these "soft" or "symbolic"
references, plus a whole chorus of people to tell you that you should
use hashes instead :-)

Ruby gives you ways to examine available existing variables, and you
can pry into them:

   @ab = "pass"
   puts instance_variable_get("@#{"a" + "b"}")

and so on.


David

-- 
                   David A. Black | dblack@wobblini.net
Author of "Ruby for Rails"   [1] | Ruby/Rails training & consultancy [3]
DABlog (DAB's Weblog)        [2] | Co-director, Ruby Central, Inc.   [4]
[1] http://www.manning.com/black | [3] http://www.rubypowerandlight.com
[2] http://dablog.rubypal.com    | [4] http://www.rubycentral.org