I'm attempting to use NSManagedObject validateForDelete in order to
provide timely feedback to delete actions by users. But the
relationship delete rules don't seem to be getting applied as I would
expect.
As a toy example I created a simple CoreData app with two entities,
Department and Employee --employees and department are the respective
inverse relationships.
The delete rule for Department employees to Employee department is
Cascade. The delete rule for Employee department to Department
employees is Nullify. I was expecting that if I had a single
Department with a single Employee, then validateForDelete would return
true on both of these managed objects. But it doesn't.
Can someone clear up my apparent misunderstanding, or suggest a better
way of accomplishing my goal? In the context of this example, if
Employee had a relationship to a third entity (say, a Stapler entity)
with a delete rule of Deny, if the user attempted to delete the
Employee's Department I would like to tell the user they must first
delete the Employee's Stapler. If they did that, then I'd like
deleting the Department to cascade to deleting the Employee.
Here's my test code:
NSManagedObject *department = [NSEntityDescription
insertNewObjectForEntityForName:@"Department"
inManagedObjectContext:moc];
NSError *error;
BOOL canDelete = [department validateForDelete:&error];
NSLog(@"1) For department canDelete = %d", canDelete);
if (! canDelete)
NSLog(@"\terror = %@", [error localizedDescription]);
NSManagedObject *employee = [NSEntityDescription
insertNewObjectForEntityForName:@"Employee" inManagedObjectContext:moc];
canDelete = [employee validateForDelete:&error];
NSLog(@"2) For employee canDelete = %d", canDelete);
if (! canDelete)
NSLog(@"\terror = %@", [error localizedDescription]);
[employee setDepartment:department];
canDelete = [department validateForDelete:&error];
NSLog(@"3) For department canDelete = %d", canDelete);
if (! canDelete)
NSLog(@"\terror = %@", [error localizedDescription]);
canDelete = [employee validateForDelete:&error];
NSLog(@"4) For employee canDelete = %d", canDelete);
if (! canDelete)
NSLog(@"\terror = %@", [error localizedDescription]);
And the resulting log output (removing the log statement data part for
brevity):
1) For department canDelete = 1
2) For employee canDelete = 1
3) For department canDelete = 0
error = Items cannot be deleted from employees.
4) For employee canDelete = 0
error = Items cannot be deleted from department.
Thanks for any help,
Ward
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