On Apr 29, 2005, at 2:32 PM, Scott Ellsworth wrote:
Faulting only applies to relationships (so in your example
comments will be loaded along with the other attributes on fetch),
and is only really relevant if you use a SQLite store since it can
fetch data on an as-needed basis. The other stores -- XML and
binary -- both load the whole persistent store into memory when
they're accessed.
What about fetched properties? The docs imply a lazy fetch, but I
have not had a chance to test.
Fetched properties are fetched lazily, then cached. If you want to
update the cache, then (as with other updates) you refault the object.
On the other hand, I am not sure I grok when I would use a fetched
property, as opposed to a stored fetch request. Is there an
implicit "must be in a relatioship with the entity that the fetched
property is a part of" condition on a fetched property, or some such?
Think of how you might represent a smart playlists in iTunes. You
could use a fetch request in place of a fetched property, but this
requires a different (and "explicit") code structure -- that is,
you'll have to retrieve the fetch request from the model then execute
it. The fetched property specifies a relationship (albeit a weak
one). It's more natural to ask a (smart) Playlist for its Tracks
than to create and execute a fetch request for Track to match a
predicate. Moreover, you then have to maintain the set of results
yourself rather than it being associated with a particular Playlist...
mmalc
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