CoreData - Adding a new relationship to existing entity

I have the following basic problem:

I have two entities, person and department.

Before adding a new person I want to check, that the department does not already exists and if so, then link the new person to the existing department.

Simple insert with a new department relationship:

    Department *department = (Department *)[NSEntityDescription insertNewObjectForEntityForName:@"Department" inManagedObjectContext:self.context];
    department.groupName = @"Office of Personnel Management";

    Person *person1 = (Person *)[NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:self.context];
    person1.name = @"John Smith";
    per开发者_JAVA百科son1.birthday = [self dateFromString:@"12-1-1901"];
    person1.department = department;

    Person *person2 = (Person *)[NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:self.context];
    person2.name = @"Jane Doe";
    person2.birthday = [self dateFromString:@"4-13-1922"];
    person2.department = department;

    department.manager = person1;
    department.members = [NSSet setWithObjects:person1, person2, nil];

the last line makes the linkage - that's ok.

But what if I want to do the following, after the execution of the code above:

    [self checkForExistingDepartment:@"Office of Personnel Management"];
    if(self.existingDepartment) {

        // here is my Problem number 1:
        // department = ???
        (NSEntityDescription *) department = self.existingDepartment;

    } else {
        Department *department = (Department *)[NSEntityDescription insertNewObjectForEntityForName:@"Department" inManagedObjectContext:self.context];
        department.groupName = @"Office of Personnel Management";

    }   

    Person *person1 = (Person *)[NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:self.context];
    person1.name = @"John Smith the second one";
    person1.birthday = [self dateFromString:@"12-1-1901"];
    person1.department = department;

    // former line for adding new: department.members = [NSSet setWithObjects:person1, nil];

    // and here is my problem number 2:
    // I think I need something like:  [NSSet addObjects:person1, nil];

In short form my problem are duplicated entries in table department.

Perhaps someone knows a good CoreData tutorial which is good for beginner with advanced SQL knowledge. (Searching on google or reading the developer documentation for hours is not that helpful as I thought :) )

For me as a beginner it's important to now whether I'm on the right way or not, can anybody confirm this?

Thanks and greetings,

matthias

You're defining the department variable inside the if/else statement and then using a different one outside of it. Try changing your if to look like :

[self checkForExistingDepartment:@"Office of Personnel Management"];
if(self.existingDepartment) {
    department = self.existingDepartment;
} else {
    department = (Department *)[NSEntityDescription insertNewObjectForEntityForName:@"Department" inManagedObjectContext:self.context];
    department.groupName = @"Office of Personnel Management";
}

Though without seeing the code for checkForExistingDepartment we can't help you very much . . .

Sorry, the check function looks like this:

- (void) checkForExistingDepartment:(NSString *)searchDepartment {
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Department" initManagedObjectContext:self.context];
    [fetchRequest setEntity:entity];
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"country" ascending:YES selector:nil];
    NSArray *descriptors = [NSArray arrayWithObject:sortDescriptor];
    [fetchRequest setSortDescriptor:descriptors];

    NSString *query = searchDepartment;
    if(query && query.length) {
        fetchRequest.predicate = [NSPredicate predicatWithFormat:@"country contains[cd] %@", query];
    }

    NSError *error;
    self.fetchedResultsController = [[NSFetchedResultsController alloc]
                                     initWithFetchRequest:fetchRequest
                                     managedObjectContext:self.context
                                       sectionNameKeyPath:@"section"
                                                cacheName:@"Root"];
    self.fetchedResultsController.delegate = self;
    [self.fetchedResultsController release];
    if(![[self fetchedResultsController] performFetch:&error]) {
        NSLog(@"Error %@", [error localizedDescription]);
    }

    self.existingDepartment = [self.fetchedResultsController objectAtIndexPath:0];
    [fetchRequest release];
    [sortDescriptor release];
}