我有一个名为“客户”的父实体。
我已经与另一个实体“Debts”
定义了一个OneToMany关系“Debts”有我的NSManagedObject类中定义的4个属性：
延期债务{
@nonobjc public class func fetchRequest() -> NSFetchRequest<Debts> {
return NSFetchRequest<Debts>(entityName: "Debts")
}
@NSManaged public var amountDebt: Double
@NSManaged public var dateDebt: NSDate?
@NSManaged public var notesDebt: String?
@NSManaged public var nameDebt: String?
@NSManaged public var debtCust: Customer?}
现在我正在尝试在桌面视图中为所有客户显示所有债务。它自己的视图控制器。
应仅为父实体制作获取请求，还是仅为子实体“债务”或两者制作？
目前，我已经尝试了父实体，但我似乎无法检索属性名称。这真让我抓狂！任何帮助将不胜感激。
我的fetchRequest：
func getFetchedResultsController() -> NSFetchedResultsController<Customer> {
frc = NSFetchedResultsController(fetchRequest: customerFetchRequest(), managedObjectContext: getContext(), sectionNameKeyPath: nil, cacheName: nil)
return (frc!)
}
func getContext () -> NSManagedObjectContext {
let appDelegate = UIApplication.shared.delegate as! AppDelegate
return appDelegate.persistentContainer.viewContext
}
func customerFetchRequest() -> NSFetchRequest<Customer> {
let fetchRequest:NSFetchRequest<NSFetchRequestResult> = NSFetchRequest(entityName: "Customer")
fetchRequest.relationshipKeyPathsForPrefetching = ["Debts"] //Not Sure about this line
let sortDescriptor = NSSortDescriptor(key: "postcode", ascending: true)
fetchRequest.sortDescriptors = [sortDescriptor]
return fetchRequest as! NSFetchRequest<Customer>
}
以上不会引发错误，但如果错误，我如何访问“债务”的各种属性
我已经尝试按照下面的指示获取“债务”，但即使保存到债务我仍未收到错误，但仍然没有结果。我怀疑我没有正确保存数据。这是我保存一对多关系的属性值的代码：
let newDebt = NSEntityDescription.entity(forEntityName: "Debts", in: context)
let debt = Debts(entity: newDebt!, insertInto: context)
debt.amountDebt = 2.50
debt.notesDebt = "Some Note"
debt.nameDebt = "Customer Name"
debt.dateDebt = Date()
cust.addToCustDebts(debt)
//save the object
do {
try context.save()
print("Save Success")
}