From: James Edward Gray II <james@...>
Date: 2006-04-29T02:45:31+09:00
Subject: Re: how to create Class object with name determined at runtime

On Apr 28, 2006, at 12:36 PM, Bill Roberts wrote:

> I hope someone can help with this - I am a Ruby newbie.
>
> In my code I want to decide at runtime which type of object to create,
> based on a variable holding the name of the class.
>
> So I have classes Foo and Bar and a string todays_class.
>
> If todays_class = "Foo"  I want to say my_obj = Foo.new
> if todayS_class = "Bar" then my_obj = Bar.new
>
> Except I've got a lot more than two classes and I'd prefer not to  
> use an
> if or case statement, so that I don't need to change the code if I add
> another one to the list.
>
> Any suggestions on a neat way to do this?

 >> class Foo; end
=> nil
 >> class Bar; end
=> nil
 >> cls = "Foo"
=> "Foo"
 >> Object.const_get(cls)
=> Foo
 >> # Or, for nested classes...
?> class Foo
 >>   class Baz; end
 >> end
=> nil
 >> cls = "Foo::Baz"
=> "Foo::Baz"
 >> cls.split("::").inject(Object) do |parent, constant|
?>   parent.const_get(constant)
 >> end
=> Foo::Baz

Hope that helps.

James Edward Gray II