From: Rob Biedenharn <Rob@...>
Date: 2007-06-16T00:14:24+09:00
Subject: Re: Dynamic Class Initialization


On Jun 15, 2007, at 10:41 AM, Enrique Comba Riepenhausen wrote:

> Hi Peer,
>
> On Friday, June 15, 2007, at 04:36PM, "Peer Allan"  
> <peer@canadadrugs.com> wrote:
>> Hi all,
>> I know this can be done, but I can't find out how to do it.  I have a
>> string with the name of the class that I want to initialize, but  
>> how do
>> I do it?
>>
>> This is what I tried,
>>
>> class = "Product"
>> product = class.new
>>
>> Obviously this does not work or I wouldn't be asking :)  So, how  
>> do I do
>> this?
>>
>> Peer
>
> Try this:
>
> clazz = Object.const_get("Product")
> product = clazz.new
>
> The word class is a reserved word so yu should use something  
> different...
>
> Cheers,
>
> Enrique

   # from Jim Weirich (based on email correspondence)
   def constantize(camel_cased_word)
     camel_cased_word.
       sub(/^::/,'').
       split("::").
       inject(Object) { |scope, name| scope.const_get(name) }
   end

Actually, Jim answered this question twice, once directly and once in  
a post to our local users group with nearly identical code, but  
clearly typed in ad hoc both times.

If you need to deal with something like ActiveRecord::Base, the  
simple form doesn't work:

 >> Object.const_get "ActiveRecord::Base"
NameError: wrong constant name ActiveRecord::Base
         from (irb):1:in `const_get'
         from (irb):1
 >> "ActiveRecord::Base".split('::').inject(Object) {|scope,name|  
scope.const_get(name)}
=> ActiveRecord::Base

-Rob


Rob Biedenharn		http://agileconsultingllc.com
Rob@AgileConsultingLLC.com