From: hochherz <hochherz@...>
Date: 2005-12-02T03:57:31+09:00
Subject: Re: abstract class

nice solution

Daniel Schierbeck wrote:
> hochherz wrote:
> 
>> hey
>>
>> is there something like abstract classes in ruby?
>> somehow a class i could not create but wich is a superclass of some 
>> classes.
>>
>> thanks
>> olaf
> 
> 
>   class Class
>     alias_method :__new__, :new
>   end
> 
>   module NonInstantiable
>     def self.included(klass)
>       super
>       klass.module_eval do
>         def self.new
>           raise "Cannot instantiate abstract class #{self}"
>         end
> 
>         def self.inherited(subklass)
>           subklass.module_eval do
>             def self.new(*args, &block)
>               __new__(*args, &block)
>             end
>           end
>         end
>       end
>     end
>   end
> 
>   class BaseKlass
>     include NonInstantiable
>   end
> 
>   class SubKlass < BaseKlass; end
> 
>   puts SubKlass.new
>   puts BaseKlass.new