[ruby-talk:5706] Re: variable variables

"Guy N. Hurst" <[e-mail]> wrote:
> A similar feature in PHP is extract(), which takes an
> associative array and puts the keys into the symbol table
> with the associaated values as the contents of each newly
> generated variable.

We call an associative array a hash (Hash), btw.

> <?php
> $arr['first']="Who";
> $arr['third']="I don't know"
> extract($arr,EXTR_OVERWRITE)	#-> $first="Who" and $third="I don't know"
> ?>
> 
> This is something I use all the time in PHP.
> 
> I'm not sure how it might work in Ruby since variables are
> not the same between the two...

You're right.  It would be damned trivial if you wanted it for only $global 
variables.  Here's a way for local variables.  Note you can't modify the 
local variables (easily?) when not local.

This is the closest I can come to doing it like PHP does without using 
(ICK!) global variables.  It's actually not that bad... kinda assumes that 
the keys in the hash will be Symbols or Strings, and you must provide the 
name of the hash to the method.

irb(main):102:0> first, third = 1, 3
[1, 3]
irb(main):103:0> x = {"third"=>"I don't know", "first"=>"Who"}
{"third"=>"I don't know", "first"=>"Who"}
irb(main):104:0> class Hash
irb(main):105:1> def extract(var)
irb(main):106:2> var = var.to_s
irb(main):107:2> t = self.collect {|k, n| "#{k} = #{var}[#{k.inspect}]"}
irb(main):108:2> t.join("\n")
irb(main):109:2> end
irb(main):110:1> end
nil
irb(main):111:0> x.extract(:x)
"third = x[\"third\"]\nfirst = x[\"first\"]"
irb(main):112:0> eval x.extract(:x)
"Who"
irb(main):113:0> puts first, third
Who
I don't know
nil



--
 Brian Fundakowski Feldman           \  FreeBSD: The Power to Serve!  /
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