From: james.d.masters@...
Date: 2007-03-15T14:35:09+09:00
Subject: General Ruby OOP Question - using inheritance or include for shared attributes

I have a generic Ruby OOP question.  Which is the more "correct" way
to share methods between two similar classes that do not necessarily
need to inherit from anything else: inheritance or include (as a mix-
in)?  I realize that this question may be subject to opinion; however,
I'm getting ready to formally release a library and I'd like to do the
"right" thing.  I like the inheritance route but I'm not sure that
creating a "Base" class that will never be instantiated directly by
anything externally is "proper".

Here are examples of both approaches:

### EXAMPLE 1 (inheritance):

# Here Base.new will (should) never be called directly; only through
inheriting classes
class Base
  def initialize()
    @records = {}
  end

  def get_record(key) ; @records[key] ; end

  def set_record(key, value) ; @records[key] = value ; end
end


class RecType1 < Base ; end
class RecType2 < Base ; end


### EXAMPLE 2 (mix-in):

module Base
  def init_record()
    @records = {}
  end

  def get_record(key) ; @records[key] ; end

  def set_record(key, value) ; @records[key] = value ; end
end

class RecType1
  include Base
  def initialize()
    init_record
  end
end

class RecType2
  include Base
  def initialize()
    init_record
  end
end


Thanks in advance,
-James