From: Robert Dober <robert.dober@...>
Date: 2007-07-12T21:05:23+09:00
Subject: Re: Abstract methods in ruby ?

On 7/12/07, James Edward Gray II <james@grayproductions.net> wrote:
> On Jul 11, 2007, at 5:40 PM, cypher.dp@gmail.com wrote:
>
> > How do you implement something like the "abstract" keyword in Java ?
> > Or: Is there a technique to force a subclass to implement a special
> > method ?
>
> One way is:
>
> class Parent
>    def abstract_method
>      raise NotImplementedError
>    end
> end
>
> You may just want to skip this step altogether though, since an
> exception toss is the default behavior.

Hmm, I would say no, you will be caught by #method_missing one day.
It would be interesting why you want to do this?

For documentation purpose? ( Dumbs up !!)

Because you want the feature? (Dumbs down ;)
I have not really yet seen a need for an abstract method in Ruby.
If you are looking for warnings or errors for subclasses not
implementing the abstract method you will be disappointed at Compile
Time [which arguabley does not even exist in 1.8]


If you are happy with the runtime exception (because you do nice code
covering tests ;) James' solution is ideal, anyway you cannot do
better  ( or worse for must of us;) in Ruby.
>
> Welcome to the word of dynamic typing.  ;)

Yes indeed, welcome :)
>
> James Edward Gray II
>
>
Robert

-- 
I always knew that one day Smalltalk would replace Java.
I just didn't know it would be called Ruby
-- Kent Beck