sectionNameKeyPath with custom CoreData model - objective-c

Question

I am working on an app, where I want to display a UITableView filled with student projects. Each project entity has several attributes like title, description, etc. and is also linked with relationships to other entities like students, study course and so on.
What I am trying to do now, is, to use the study courses as sections in which are all the respective projects which are made by students from that study course.
So far, my code looks like this
- (NSFetchedResultsController *)fetchedResultsController
{
if (_fetchedResultsController != nil) {
return _fetchedResultsController;
}
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Project" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
[fetchRequest setFetchBatchSize:20];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"title" ascending:YES];
NSArray *sortDescriptors = #[sortDescriptor];
[fetchRequest setSortDescriptors:sortDescriptors];
NSFetchedResultsController *aFetchedResultsController =
[[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
managedObjectContext:self.managedObjectContext
sectionNameKeyPath:Nil
cacheName:Nil];
aFetchedResultsController.delegate = self;
self.fetchedResultsController = aFetchedResultsController;
return _fetchedResultsController;
}
and this is a screenshot of the CoreData model.
I am really new to Obj-C and haven't designed the data model myself, so I'm kind of lost here and would be really glad about any help.

Answer 1

You haven't asked a specific question yet, but I can give you some basic direction. The way you're creating your NSFetchedResultsController looks correct except that you need to do two more things: sort the result by course title and set the sectionNameKeyPath to course title (I'm assuming your Studycourse entity has a title property, but substitute another property as needed).
- (NSFetchedResultsController *)fetchedResultsController
{
...
NSSortDescriptor *courseTitleSortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"projecttostudycourse.title" ascending:YES];
NSSortDescriptor *titleSortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"title" ascending:YES];
NSArray *sortDescriptors = #[courseTitleSortDescriptor, titleSortDescriptor];
[fetchRequest setSortDescriptors:sortDescriptors];
NSFetchedResultsController *aFetchedResultsController =
[[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
managedObjectContext:self.managedObjectContext
sectionNameKeyPath:#"projecttostudycourse.title"
cacheName:Nil];
...
}
Note that by providing two sort descriptors, the projects will first be organized by course and then, within each corse, by project title. The other thing worth noting is that key paths use dot notation to follow entity relationships. So the way to reach the course title from a project entity is #"projecttostudycourse.title".