From: Pit Capitain <pit@...>
Date: 2005-07-08T06:00:00+09:00
Subject: Re: Struct-like behaviour in custom classes

Levin Alexander schrieb:
> How can I build a Class that works like the built-in "Struct" and 
> returns  new anonymous classes based on arguments to MyClass.new?
> 
> A simplified example:
> 
>   with_foo = MyClass.new(:foo)
>   one = with_foo.new
>   one.foo
> 
>   with_bar = MyClass.new(:bar)
>   two = with_bar.new
>   two.bar
> 
> I tried to do:
> 
>   class MyClass
>     def self.new_class(method_name)
>       c = Class.new(self)
>     c.class_eval do
>       define_method(method_name) { puts "method #{method_name} called" }
>     end
>       return c
>     end
>   end
> 
> How can I rename 'new_class' to 'new' without breaking 'new' in 
> derieved  classes?

Hi Levin,

you have to redefine "new" in the anonymous classes to call the original 
Class.new method. One possibility is to use aliases:

   class MyClass
     class << self
       alias :org_new :new
       def new(method_name)
         Class.new(self) do
           class << self
             alias :new :org_new
           end
           define_method(method_name) do
             puts "method #{method_name} called"
           end
         end
       end
     end
   end

Regards,
Pit