From: Christopher <christopher.carroll@...>
Date: 2005-04-30T03:36:11+09:00
Subject: Re: Creating arbitrary objects

On Sat, 2005-04-30 at 03:05 +0900, James Edward Gray II wrote:
> On Apr 29, 2005, at 12:38 PM, Matthew Thill wrote:
> 
> > I've probably overlooked something, and hopefully someone can help me 
> > out. I want to be able to create arbitrary object from the contents of 
> > a string.
> >
> > For example, if I had the following string:
> >
> > classname = "Array"
> >
> > How can I create an Array object, knowing only that the variable 
> > classname held the name of some class as a string.
> 
> You're looking for Object.const_get():
> 
> irb(main):003:0> class_obj = Object.const_get("Array")
> => Array
> irb(main):004:0> arr = class_obj.new
> => []
> 
> Hope that helps.
> 
> James Edward Gray II
> 
> 
> 

If your class is nested in a module or other class, you might want to do
something like:

irb:0> module A
irb:1>     class B
irb:2>         class C
irb:3>         end
irb:2>     end
irb:1> end
=> nil
irb:0> classname = 'A::B::C'
=> "A::B::C"
irb:0> klass = classname.split('::').inject(Class) do |sum, elem|
irb:1*     sum.const_get(elem)
irb:1> end
=> A::B::C
irb:0> klass.new
=> #<A::B::C:0xb7d12640>