Question

I have two core data entities. Lets call them AAA and BBB.

BBB contains a relationship to AAA, one to one.

When I create a new BBB entry, I do (at this point myA is one entry on AAA):

BBB *item = nil;
NSFetchRequest *request = [[NSFetchRequest alloc] init];
request.entity = [NSEntityDescription entityForName:@"BBB" inManagedObjectContext:context];

request.predicate = [NSPredicate predicateWithFormat:@"(relation == %@)", myA];

NSError *error = nil;
item = [[context executeFetchRequest:request error:&error] lastObject];
[request release];

if (!error && !umItem) {  // if there's no item, create a new one
    item = [NSEntityDescription insertNewObjectForEntityForName:@"BBB" inManagedObjectContext:context];
    item.relation = myA;  // to create a relation from BBB to AAA
}

at some point in time, I have just a list of BBB objects. Remember that each BBB object has a property called relation pointing to AAA.

Now, how do I retrieve AAA?

Is it enough to do

AAA *myAAA = (AAA*)myBBB.relation;

is this relation the object itself on AAA?

how do I do that?
thanks

Answer 1

Yes, by calling myBBB.relation; (dynamic typing is not needful if relation is of type AAA) you will get object of class AAA or nil. If relation is not optional then before committing changes you should define that relationship to all updated/new objects.