From: james@...
Date: 2002-07-05T08:40:34+09:00
Subject: RE: self_parent

>
> all my real examples are pretty large, mostly to do with using the REXML
> stream parser. also the utility of this really only becaomes significant
> when the program is substatial. if you only have one or two variables to
> worry about it's easy enough to just pass those. but if you need access
> to a handful or more, and perhaps some of the parents methods, then this
> becomes a wonderful convience.

How would an object know the methods of an arbitray parent?  Doesn't this
completly couple the two objects? The parent (reasonably) expects the
object it creates to implement certain methods; the newly-created object
expects the parent to implement certain methods.

Perhaps I misunderstand what you need to accomplish or how self_parent
would be implemented, but it sounds like it would encourage fragile designs
without any real gains.

In your example, Address requires an object that implements pretty_name.
It works with any parent if that parent passes in a pretty_name-compliant
object.  Having Address use self_parent means it *only* works when the
parent responds (and in the right way) to pretty_name.  Changing the
Customer class can break the Address class, and vice versa.


James