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I'm making another push to convert Mailman from Python pickles to SA,
essentially starting over from scratch (on the SA side, I'm try to
rewrite as little of Mailman as possible). So far so good; I've
mostly been able to overcome the few glitches along the way. I'm
still in the early stages, but I think I now need to use a mapper
extensions and I have some questions about it.
In classic Mailman, the central MailList class loads a pickled
dictionary in its constructor and sets attributes on self
corresponding to the keys/values found there. This part is fairly
easy to just rip out and let SA do its magic.
However the other thing that happens in the MailList ctor is that we
call a method InitTempVars() which gives each of the mixin base
classes a chance to set some volatile attributes (i.e. non-
persistent). On the positive side, those attributes are all non-
public and start with an underscore. The problem though is that when
SA instantiates a MailList in response to a query, my InitTempVars()
methods obviously won't get called.
Enter the mapper extension. The first thing I noticed is that the
documentation for MapperExtension.create_instance() is incorrect. It
only describes 4 arguments (plus self), but in SA 0.3.x, that method
takes 5 arguments. I found the proper signature in an example in the
FAQ, but the question is what is the 'imap' argument?
So what I really want is that the regular SA magic happens and I just
do a little work (calling InitTempVars()) either before or after
that. I'm not sure about the best way to do this. Will SA populate
the object I return from create_instance() with the row data or do I
have to do that myself?
The other thing is that InitTempVars() requires one argument, which
can be calculated from data in the row. That's fine because the row
is passed to create_instance(), but it looks weird. If I dump out
the keys of the row object, they look like column names with the
lower cased table name prepended. E.g. the columns I need are
list_name and host_name but the corresponding keys in the row object
are listdata_list_name and listdata_host_name ('Listdata' being the
name of my table). I'm not sure if this is the intention or if
there's a better way to get the row data out in create_instance().
Thanks in advance,
- -Barry
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