[Zope-CMF] Need advice on sorting my custom CMF object

[Dieter Maurer]

Lynn Walton writes:
 > ....
 > My question is in regard to sorting. I want to sort on the postdate
 > which will be a DateTime() object.  I don't know what my options are and
 > what is "better". Trying to add an index to the portal catalog for my
 > CMF type and it's postdate attribute? If so, I'm not sure how to do
 > that.   I don't anticipate there ever being more than 20 Job Postings in
 > each of the three folders so I'm guessing it isn't worth doing it with
 > the portal catalog.   I read somewhere where zpt's don't have the sort
 > feature that dtml-in does.
When your result list could be large (and you were using batching),
then it would definitely be better to delegate the sorting to
the catalog.

But as your result lists are small, this may not be necessary
(though probably still the easiest solution).

I see three options:

  1.  index your attribute in "portal_catalog"

      go to the "Indexes" tab of "portal_catalog" and
      add a "FieldIndex" with your attribute's name

      Use the "sort_on" parameter of the catalog's search
      method to let it sort

  2.  Sort with the versatile "sequence.sort" function.
      You find a description in ".../DocumentTemplate/sequence/SortEx.py".

      There a two variants:

        a)  define your attribute as a Metadata element (-->
	    "Metadata" tab) of "portal_catalog".

	    Then, during cataloging, the value is stored
	    in the catalog and available in the result
	    rows for catalog queries.

	    You do not need to provide your own
	    comparison function but can simply tell
	    "sequence.sort" to sort on this attribute.

	b)  you do not modify "portal_catalog".

	    Then the result returned by a search does not
	    know about your attribute. It is necessary
	    to fetch the object (---> getObject) and
	    ask it for its attribute value.

	    This requires either a specific comparison function
	    or preprocessing the query result (calling
	    "getobject" on each of them and sorting the resulting
	    list).

Dieter