[Zope] Re: Modifying __bases__

[Derrick Hudson]

On Fri, May 20, 2005 at 05:10:30PM -0400, Dan Pozmanter wrote:
| Out of curiosity, I've noticed the word "evil" attached to patching
| of various and monkey kinds.  Not "bad", or "unwise", but "evil",
| implying a morality associated with the act.

I think it is used mainly to give added emphasis to lessons learned
from painful experience.  As Paul reported, hours can be wasted
tracing the wrong code trying to understand what is happening.

| What is morally wrong with modifying live objects in a dynamic language
| to achieve desired functionality?

The problem is maintainability.  When you dynamically rewrite the
code, the code is then very difficult to follow, verify, and modify.
It is even harder for someone else to maintain the code because they
don't have the historical background to rememeber where , what and why
the code is dynamically changed.

| The idea is "I want to modify the zope core in a way that survives
| version to version, yet does not
| impose a specific use case on all zope users".

The good pattern for handling this is to create a new class that
extends the core classes that provide almost the functionality you
want.  Then, in your part of the database, create an instance of your
class instead of the built-in core class.

Specifically for your case, extend the basic UserFolder class to
create instances of your custom User class instead of the built-in
one.  It would be good if the UserFolder allowed you to parameterize
it so you could simply say "use this User class", but in the absence
of that foresight, you can extend the UserFolder clas.

HTH,
-D

-- 
Whoever loves discipline loves knowledge,
but he who hates correction is stupid.
        Proverbs 12:1
 
www: http://dman13.dyndns.org/~dman/            jabber: dman at dman13.dyndns.org
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