Re: [SQLObject] Reimplements the constructor...

[Luke O. <lu...@me...>]

> I want to reimplement the constructor to know when I adding the article
> in a section or in a title, so, if the user adding in a section, I can
> get the title from the section, the article will always have a title,
> even if it is in a section...
>
> Is it a good idea? Thanks for any help and sorry about my poor english :)

I may be misunderstanding you, is article.title a ForeignKey to title that may
be NULL (when the title comes from article.section)? If so, from a database
perspective I would not duplicate the data to set article.title =
article.section.title. If section.title changes, then you need more
application code to correctly update the article title, etc.

Instead, transparently retrieve the section's title if the article has no
title:

class Article(sqlobject):
  title = ForeignKey('Title', default=None)
  section = ForeignKey('Section', default=None)
  ..

  def _get_title(self):
    storedTitle = self._SO_get_title()
    if storedTitle:
      return storedTitle
    else if self.section:
      return self.section.title
    else:
      return None

a = Article(section=aSection, ...)
a.title   # returns aSection.title
a.title = aTitle
a.title   # returns aTitle

Logic may not be exactly how you need it (which has precedence if an article
has both a title and a section?), but I would generally solve this in this
way: leave the data model clean and get the behavior I want by overriding the
properties. (See
http://www.sqlobject.org/docs/SQLObject.html#overriding-column-attributes if
the _get_columnName thing is unfamiliar.)

- Luke