Re: Fetching entities where the relations are known (rakel)

  • Ok, it was easy:

    NSArray *variables = [ variablesController arrangedObjects ];
    NSManagedObject *variable = [ variables objectAtIndex:
    [ variablesController selectionIndex ] ];

    (next time I'll try some more before posting a question...)

    /Dan

    12 okt 2006 kl. 14.04 skrev rakel:

    > The reason the predicate didn't work, was that my currentPerson
    > object was NOT the NSManagedObject instance I thought it was, it
    > was a proxy (an instance of the class _NSControllerObjectProxy as
    > it turned out) which I received from the selection in an
    > NSArrayController. (According to the documentation it shall be
    > possible to use the predicate I described, but this of course
    > requires the correct objects :-)
    >
    > Now, the question is as follows, given an NSPopUpButton, bound to
    > an NSArrayController which in turn is bound to a
    > ManagedObjectContext, how do I get an NSManagedObject instance
    > corresponding to the selected item in the popup?
    >
    > Regards/Dan
    >
    >> Från: rakel <rakel...>
    >> Datum: tisdag 10 okt 2006 23.13.06 GMT+02:00
    >> Till: <cocoa-dev...>
    >> Ämne: Fetching entities where the relations are known
    >>
    >>
    >> I have a Core Data model, which looks something like [Person] ----
    >> * [Value] *---- [Variable] I.e. the Person entity has a to-many
    >> relation to the Value entity, and the Variable entity also has a
    >> to-many relation to Value. Value in turn has a to-one relation
    >> with both Person and Variable (and before anyone asks, no, this is
    >> not a "many to many"-relational table as seen in ordinary
    >> relational databases).
    >>
    >> Also, the Value entity has a date attribute, called assessmentDate.
    >>
    >> Now, in my application I have a Person instance and a Variable
    >> instance. How do I get all the corresponding Value instances,
    >> sorted on assessmentDate?
    >>
    >> I have been trying around with fetch predicates, with no success
    >> ( [NSPredicate predicateWithFormat:@"personr == %@",
    >> currentPerson ] does not do the trick). Another idea could be to
    >> ask the Person for the set of all its Values and then the Variable
    >> for the set of all its Values, and then to take the union of those
    >> two sets -- but this won't sort the Values.
    >>
    >> Regards /Dan
    >>
    >
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