Swift 4 Core Data - Fetching Relationships - core-data

Question

I have entities as so:
Entity 1
Entity 2
I am saving data as so:
#IBAction func saveButton(_ sender: UIButton) {
print("save")
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {
return
}
let context = appDelegate.persistentContainer.viewContext
let workout = Workout(context: context)
workout.name = workoutName.text
workout.noOfSets = Int16(setsStepper.value)
for index in 0..<setsVal {
let sets = Sets(context: context)
let test = IndexPath(row: index, section: 0)
let cell = tableView.cellForRow(at: test) as! RepsTableViewCell
sets.repAmount = Int16(cell.repsStepper.value)
// Does this line not create the relationship between Workout and Set Entities?
workout.addToSets(sets)
}
try! context.save()
}
And I am fetching data as so:
func fetch() {
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {
return
}
let context = appDelegate.persistentContainer.viewContext
let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Workout")
request.relationshipKeyPathsForPrefetching = ["Sets"]
do {
let result = try context.fetch(request)
for data in result as! [NSManagedObject] {
print(data.value(forKey: "name") as! String)
print(data.value(forKey: "noOfSets") as! Int16)
}
}
catch {
print("failed")
}
}
I've set up the relationship between entities Workout and Sets as one-many, yet cannot retrieve Set's attributes from Workout.
How can I retrieve an entities relationship attributes?
Do I need to specify the relationship programmatically despite the relationship being setup in the xcdatamodel file?
Does Workout.addToSets(sets) create the relationship between the entities?

Answer 1

You should be able to access your relationship entities as an attribute so for instance
for workout in result as! [Workout] {
print(workout.name)
if let sets = workout.sets { //assuming you have name your to-many relationship 'sets'
print(sets.count)
}
}