Re: Method type 'abstract'

In article <00e001c1c9e8$18a97940$0700000a@backpack>,
Nat Pryce <[e-mail]> wrote:
>From: "Peter Hickman" <[e-mail]>
>> At present I have to insert a normal method in the class that raises an
>> exception which will then cause the subclass to fall over if it did not
>> override it. It works but it isn't clean, to my mind abstract is just as
>> fundemental as public or private and therefore should be marked as such.
>
>Why not just *not* implement the method at all and let method_missing throw
>the exception for you?
>

That would be a problem in classes where you define method_missing for 
some other use.

I'm content with throwing an exception in methods that are 'abstract' (ie. 
methods that should be overridden by subclasses), but perhaps we can make 
that easier by defining an 'abstract' method within Module, like:

#NOTE: I have not tried this code, it probably doesn't work!!!
class AbstractException < Exception
end

class Module
  def abstract(*symbols)
    symbols.each { |s|
      instance_eval("def #{s}; raise AbstractException \"#{s} must be 
overridden!\";end")
    }
  end
end
  

class MyClass

  abstract :some_method

end

mc = MyClass.new
mc.some_method #=> "some_method must be overridden!"


I'm not proposing this as an RCR, just as an idea that could be used to 
acheive what the original poster wants to do.

Phil