From: Florian Gross <flgr@...>
Date: 2005-01-12T21:01:17+09:00
Subject: Re: Kernel#eval and class definition

Yukihiro Matsumoto wrote:

> |>     def f ; class C ; end ; end
> |>     def f ; eval "class C ; end", binding ; end
> |
> |Well eval "..." is just an expression and "eval" evaluates everyhing it
> |get's that's syntactically correct.  The ruby code in the string
> |expression is not syntactically located in method f.  It's parsed at
> |runtime while the line above is completely evaluated at compile time.
> 
> Thanks for explanation.  class definition in the method is prohibited
> by syntax just to detect errors.  And class definition in eval is
> allowed as a back door.  Besides, scope management also is a reason,
> but it's an implementation matter.

There's also Class.new which will create an anonymous class. You can 
assign that to a constant via Module#const_set if you need to have a 
named class for some reason. That might be a bit better than using 
eval() depending on the use case.