The answer depends on your definition of “decent”. There is nothing in EOF,
and nothing that I am aware of in Wonder that will do this. To achieve this
you need to:
1. Write the access method like yo have below, but cache the result for
performance.
2. Write the mutator methods (if you need them) to work on the original
EOF relationship
3. Modify the mutator methods of the original relationship to either
invalidate or update this cache (update is faster but harder to write)
4. Intercept certain EOF operations/notifications so that the cache can
be updated or invalidated when EOF changes the underlying snapshots
I can dig the details for (4) out for you if you want to pursue this.
Chuck
From: <webobjects-dev-bounces+chill=gevityinc....@lists.apple.com> on behalf of
OC <o...@ocs.cz>
Date: Friday, July 8, 2016 at 1:11 AM
To: WebObjects-Dev Mailing List <webobjects-dev@lists.apple.com>
Subject: qualified to-many relationships?
Hi there,
is there a way to define and use a to-many relationship, derived from a
modelled one, by limiting the results by a qualifier?
I have got an entity, say, "DBTable", whose to-many relationship "records"
returns a set of eos of entity "DBRecord". That works all right.
Now, I need to implement a "qualifiedRecords" relationship, which would work
this way:
===
class DBTable ... {
NSArray qualifiedRecords {
EOQualifier qq=ERXSession.session().recordQualifier; // the qualifier
depends on current user and other conditions of the current session
return EOQualifier.filteredArrayWithQualifier(this.records(),qq);
}
}
===
With small objects, I would use precisely the code above. Alas, my DBTables
contain _lots_ of DBRecords, and thus the above implementation would get
terribly slow by fetching all of them and then re-filtering them each time the
relationship is accessed.
What I need here is same behaviour functionality-wise, but at a lower level,
sort of like EODatabaseDataSource's auxiliaryQualifier, but somehow bound to
the particular relationship, so that
(a) it is not needed to fetch all records -- the "qualifiedRecords"
relationship would, when fired, automatically fetch only the qualified ones
(b) records are fetched once and then cached, just like it is with normal
relationships
(c) I can use things like
ERXEOControlUtilities.objectCountForToManyRelationship(sometable,"qualifiedRecords")
etc. seamlessly, and they work as expected.
Is there a way to do this at all? Perhaps I am just blind, but I cannot find
any decent solution :/
Thanks and all the best,
OC
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