[Zope] Persistent dictionaries

24 Aug 2001

      Hi

I'm working on a CMF Product which is based on PortalFolder and 
PortalContent. This Folderish object contains some items which inherits from 
OFS.SimpleItem.Item, Persistence.Persistent and Aquisition.Implicit.
These items have (had) some properties which are speciel to their class. In 
order to get around the problem with adding new attributes and having 
instantiated objects which doesn't have the attributes I decided to keep the 
attributes in a dictionary. So in my base class I did:

---snip--------------------------------------------
class AbstractElement(Persistent, Item, Implicit):
    """ Abstract base class for Element objects. """
    _attributes = PersistentMapping()

    def __getattr__(self, name):
        if self._attributes.has_key(name):
            return self._attributes[name]
        else:
            raise AttributeError, name
---snip--------------------------------------------

and my derived classes look something like this:

---snip--------------------------------------------
class TextElement(AbstractElement):
    """
    text element.
    """
    meta_type = 'Text Element'

    def __init__(self, id):
        self.id = id
        self._attributes = {'value':'','html':'','alignment':''}

    def edit(self, value, html, alignment):
        """ Update the properties """
        self._attributes['alignment'] = str(alignment)
        self._attributes['value'] = str(value)
        self._attributes['html'] = utils._format_stx(self.value)
---snip--------------------------------------------

It works great - until the object gets unloaded from the memory :-(

What am I doing wrong?

-- 
Regards,
	Thomas Olsen

http://www.tanghus.dk