Removal of core data object does not nullify all of its relations?

Question

I have an entity called Task which has a to-one relationship with the entities TaskTemplate and Occurrence. Both of these entities have to-many relationships with Tasks. Deletion rules are set to Nullify.

Within an Occurrence, I try to remove all Tasks. To do that, I use the following code:

- (bool)removeAllTasks
{
    NSMutableSet *tasks = [self mutableSetValueForKey:@"tasks"];
    [tasks removeAllObjects];
    return YES;
}

This does not work. Here are Task and Occurrence before the attempted removal:

Relationship 'tasks' on managed object (0x1006bd1c0) <Occurrence: 0x1006bd1c0> (entity: Occurrence; id: 0x102119510 <x-coredata://6A0ECEF9-473D-44B2-9E89-AC15179D7761/Occurrence/p1> ; data: {
    ... bunch of properties ...
    taskType = "0x10211a020 <x-coredata://6A0ECEF9-473D-44B2-9E89-AC15179D7761/TaskTemplate/p2>";
    tasks =     (
        "0x1021185e0 <x-coredata://6A0ECEF9-473D-44B2-9E89-AC15179D7761/Task/p3>"
    );
}) with objects {(
    <Task: 0x10c31d700> (entity: Task; id: 0x1021185e0 <x-coredata://6A0ECEF9-473D-44B2-9E89-AC15179D7761/Task/p3> ; data: {
    ... some more properties ...
    occurrence = "0x102119510 <x-coredata://6A0ECEF9-473D-44B2-9E89-AC15179D7761/Occurrence/p1>";
    persons = "<relationship fault: 0x10e049e90 'persons'>";
    startDate = "2013-01-28 11:00:00 +0000";
    type = "0x10211a020 <x-coredata://6A0ECEF9-473D-44B2-9E89-AC15179D7761/TaskTemplate/p2>";
})
)}

... and this is the result after -removeAllObjects:

Relationship 'tasks' on managed object (0x1006bd1c0) <Occurrence: 0x1006bd1c0> (entity: Occurrence; id: 0x102119510 <x-coredata://6A0ECEF9-473D-44B2-9E89-AC15179D7761/Occurrence/p1> ; data: {
    ... bunch of properties ...
    taskType = "0x10211a020 <x-coredata://6A0ECEF9-473D-44B2-9E89-AC15179D7761/TaskTemplate/p2>";
    tasks =     (
    );
}) with objects {(
)}

Notice that the tasks relationship is now empty, as I would expect it to be. But I would also expect taskType to be empty. What am I doing wrong?

EDIT:

I changed the code so I can see if the task is marked as deleted. I have now:

- (bool)removeAllEvents
{
    NSMutableSet *tasks = [self mutableSetValueForKey:@"tasks"];
    [tasks enumerateObjectsUsingBlock:^(Task *task, BOOL *stop)
     {
    if (![task isDeleted])
         [self.managedObjectContext deleteObject:task];
         NSLog(@"Deleted %@", [task isDeleted] ? @"Y" : @"N");
     }];
    [self.managedObjectContext processPendingChanges];
    return YES;
}

It does show 'Y', to indicate that the task is marked for deletion. A fetchRequest shows me that there are no tasks left in the context. But if I try to save, I get an inconsistency message ("tasks is not valid").

Answer 1

Your removeAllTasks method does not delete any objects. It only removes the relationships from the Occurrence object to the Task objects, but the tasks continue to exist. The deletion rules are only applied if an object is deleted (using deleteObject:).