I just recently bought and digested Object-Oriented Perl by fellow australian, damian conway. great book.

Even after musing over damian's insights, dare i say that OO programming in perl could still be implemented much more cleanly/elegantly (IMHO).

On that note, i am searching for enlightened monks' opinions on the best way to implement class data such that it may be cleanly inherited by subclasses.

here are (my) 2 top contenders:

• As a method with void prototype:
  

  my $_Class_Data = "private stuff";
  ...
  sub Class_Data () { return $_Class_Data; }
  [download]

  On the surface this appears the best solution: it is inherited, and may be subclassed; though therein lies its downfall - a subclass is obligated to provide its own implementation of Class_Data if it wants to expose its own version of $_Class_Data. not an ideal solution when you want a subclass to provide its own $_Class_Data without requiring the subclass author to provide an implementation.

• Storing a reference to class data a la tchrist.
  

  my $_Class_Data = "private";
  ...
  # constructor
  sub new 
  {
      my $class = shift; 
      return bless(
          {    _Class_Data => \$_Class_Data,
              # other init...    
          },
          $class
      );
  }
  [download]

  This approach works fine if you only want to provide $_Class_Data only from the class in which $_Class_Data was first declared, *and* if you provide an accessor method for it, or note it as "public class data" in the object hash. If you really want to have each class have its *own* version of $_Class_Data, you're out of luck.

So, opinions anyone? I can see that it wouldn't be too difficult to provide a Class_Data method which accessed/ manipulated the namespace of the calling object's classname, but that's *really* pushing the limits of what most people accept as "OO abstraction".

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