From: rbaldwin <ryan.baldwin@...>
Date: 2007-12-13T09:54:59+09:00
Subject: Re: Abstract -- what's the Ruby way?

On Dec 12, 5:10 pm, "Tim Rowe" <n...@digitig.co.uk> wrote:
> What's the Ruby way to define a class that shouldn't be instantiated, but
> with descendants that can be? Other than a comment in the documentation, of
> course.
>
> Thanks!

Here is one way. Its not very satisfying, as you have no way to access
the initialize method on any parent classes of the Animal class (such
as ActiveRecord)...

class Animal

  def initialize
    raise 'Invalid instantiation of class'
  end

  def talk
    puts 'hi'
  end

end

class Dog < Animal

  def initialize
      # this can be empty
      # don't use super here as will cause exception from Animal
  end

end

# this will fail (as it should) with an exception
# a = Animal.new

# this succeeds
d = Dog.new
d.talk