Core data Relationship in swift - ios

Question

I am working on iPhone application where I need to implement one to many relationship from one entity to another entity.I have export NSManagedObject subclass from coredata database but could not find relation accessors in core data model file like Objective-C.
Although I'm able to set data in relationship NSSet but this only persist while iPhone app is running. Once I kill and restart the application I didn't get entity relationship for in fetch request from core data.
I am not sure what I am doing wrong. It will be great if anyone can tell me how to set data in NSSet relationship object. Any sample example will be a great help
Here is my core data model files. One folder can content multiple content as folder detail
extension FolderContent {
#NSManaged var contentID: NSNumber?
#NSManaged var contentTitle: String?
#NSManaged var contentType: String?
#NSManaged var publishDate: String?
#NSManaged var folderList: NSSet?
}
extension FolderList {
#NSManaged var folderID: NSNumber?
#NSManaged var folderName: String?
#NSManaged var folderDetail: NSSet?
}
func updateFolderList()
{
// Initialize Fetch Request
let fetchRequest = NSFetchRequest()
// Create Entity Description
let entityDescription = NSEntityDescription.entityForName(FOLDER_LIST, inManagedObjectContext: self.managedObjectContext)
// Configure Fetch Request
fetchRequest.entity = entityDescription
do {
let result = try self.managedObjectContext.executeFetchRequest(fetchRequest).last as! FolderList
let content = result.mutableSetValueForKey("folderDetail")
content.addObject(self.getContent())
var folderContent:FolderContent = result.folderDetail?.allObjects.first as! FolderContent
print(folderContent.contentTitle)
self.save()
print(result)
} catch {
let fetchError = error as NSError
print(fetchError)
}
}
func getContent()->FolderContent
{
let folderContent = NSEntityDescription.insertNewObjectForEntityForName(FOLDER_CONTENT, inManagedObjectContext: self.managedObjectContext) as! FolderContent
folderContent.contentID = 1
folderContent.contentTitle = "Sandeep"
folderContent.contentType = "Product"
return folderContent
}

Answer 1

If the relationship of FolderContent and FolderList is defined as
A FolderContent have many FolderList(s)
A FolderList only belongs to a FolderContent
FolderContent
extension FolderContent {
#NSManaged var contentID: NSNumber?
#NSManaged var contentTitle: String?
#NSManaged var contentType: String?
#NSManaged var publishDate: String?
#NSManaged var folderList: Set<FolderList>?
}
FolderList
extension FolderList {
#NSManaged var folderID: NSNumber?
#NSManaged var folderName: String?
#NSManaged var folderDetail: FolderContent?
}
Let say you want to persist the record and its relationship
func persistRecords() {
// Insert the new records
let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
let managedContext = appDelegate.managedObjectContext
let folderContentEntity = NSEntityDescription.entityForName("FolderContent", inManagedObjectContext: managedContext)
let folderListEntity = NSEntityDescription.entityForName("FolderList", inManagedObjectContext: managedContext)
//Create FolderContent record
let folderContentObject = FolderContent(entity: folderContentEntity!, insertIntoManagedObjectContext: managedContext)
folderContentObject.setValue(CONTENTID, forKeyPath: "contentID")
...
//Create FolderList record
let folderListObject = FolderList(entity: folderListEntity!, insertIntoManagedObjectContext: managedContext)
folderListObject.setValue(FOLDERID, forKeyPath: "folderID")
...
//Set relationship here
folderListObject.folderDetail = folderContentObject
do {
try managedContext.save()
} catch let error as NSError {
print("Could not save \(error), \(error.userInfo)")
}
}

Answer 2

I am guessing you did something like folder.folderDetail.addObject. With core data that won't work because core data behind the scenes is doing lots of things to maintain graph integrity. You have to use mutableSetValueForKey to get the set and have core data work its magic.