I get this error: fatal error: unexpectedly found nil while unwrapping an Optional value
In this function:
func textFieldShouldReturn(textField: UITextField) -> Bool {
tableViewData.append(textField.text)
textField.text = ""
self.tableView.reloadData()
textField.resignFirstResponder()
// Reference to our app delegate
let appDel: AppDelegate = UIApplication.sharedApplication().delegate as AppDelegate
// Reference moc
let contxt: NSManagedObjectContext = appDel.managedObjectContext!
let en = NSEntityDescription.entityForName("note", inManagedObjectContext: contxt)
// Create instance of pur data model an initialize
var newNote = Model(entity: en!, insertIntoManagedObjectContext: contxt)
// Map our properties
newNote.note = textField.text
// Save our context
contxt.save(nil)
println(newNote)
// navigate back to root vc
//self.navigationController?.popToRootViewControllerAnimated(true)
return true
}
and this line of code:
var newNote = Model(entity: en!, insertIntoManagedObjectContext: contxt)
Does someone have a solution for this error?
I use xCode 6.0.1. Programing language is Swift and the Simulator runs with iOS8 (iPhone 5s).
NSEntityDescription.entityForName("note", inManagedObjectContext: contxt) returns an NSEntityDescription?. So it is optional and can be nil. When you force to unwrap it (with ! operator) if it is nil then your program crashes. In order to avoid this you can if-let syntax. Here is how:
if let entity = NSEntityDescription.entityForName("note", inManagedObjectContext: contxt) {
// Do your stuff in here with entity. It is not nil.
}
However in Core Data cause of the entity become nil is maybe you spell the name "note" wrong. Check your xcdatamodel file.
That error happens when you unwrap an optional which contains nil. If that's the line causing the error, then it's the en variable set to nil, and you are trying to force unwrap it.
I cannot provide a reason for it to be nil, but I suggest to avoid using forced unwrapping (i.e. using the ! operator), and rely on optional binding instead:
if let en = en {
var newNote = Model(entity: en, insertIntoManagedObjectContext: contxt)
// Map our properties
newNote.note = textField.text
// Save our context
contxt.save(nil)
println(newNote)
}
That solves the exception. You should investigate on why en is nil though.
Related
I want to set up a mock for my Core data manager.
I'm doing this the old way for the core data stack, but want to do it for the exercise.
In the main Core Data Manager I set up with
var objectContext: NSManagedObjectContext! = nil
var entity: NSEntityDescription! = nil
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else { return }
objectContext = appDelegate.persistentContainer.viewContext
entity = NSEntityDescription.entity(forEntityName: Constants.entityName, in: objectContext)!
Now obviously I can't use UIApplication's persistent container in my mock.
So I tried to use the following:
objectContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
let entityOne = NSEntityDescription.insertNewObject(forEntityName: Constants.entityName, into: objectContext)
However I get the error "NSInvalidArgumentException", "+entityForName: nil is not a legal NSPersistentStoreCoordinator for searching for entity name 'TaskEntity'"
So how can I set a new objectContext for my mock?
One solution is to create a full Core Data stack but let the persistent store reside in memory only. This way you don't have to deal with some app delegate dependency. Set context to nil and remove the store from the coordinator afterwards in tearDown()
class TestExample: XCTestCase {
var storeCordinator: NSPersistentStoreCoordinator!
var managedObjectContext: NSManagedObjectContext!
var managedObjectModel: NSManagedObjectModel!
var store: NSPersistentStore!
override func setUp() {
super.setUp()
managedObjectModel = NSManagedObjectModel.mergedModel(from: nil)
storeCordinator = NSPersistentStoreCoordinator(managedObjectModel: managedObjectModel)
do {
store = try storeCordinator.addPersistentStore(
ofType: NSInMemoryStoreType, configurationName: nil, at: nil, options: nil)
} catch {
XCTFail("Failed to create a persistent store, \(error)")
}
managedObjectContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
managedObjectContext.persistentStoreCoordinator = storeCordinator
}
developing a little app for my comic collection encountered this issue:
in my second "add comic" VC I have a button and the func below, but I save TWICE entities in manged context (ate least, I think this is the issue)
for example if I have 2 comics yet shown in main VC tableview, go to "add comic VC" and save a third one, going back to main VC I'll print 3 objects with title, number etc but also print 2 new objects with no data as I had saved twice a manger context a "right one" and another one with same number of object but empty. If I keep adding a 4th comic, I'll get 6 complete comic + the 4th and more 6 "blank itmes" with default values "no title"
let kComicEntityName = "Comic"
func addingSingleComic(gotTitle: String, gotIssue: Int16, gotInCollection: Bool ) {
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {return}
let managedContext = appDelegate.persistentContainer.viewContext
let entity = NSEntityDescription.entity(forEntityName: kComicEntityName, in: managedContext)!
let comicToAdd = Comic(entity: entity, insertInto: managedContext)
comicToAdd.comicTitle = gotTitle
comicToAdd.issueNumber = gotIssue
comicToAdd.inCollection = gotInCollection
do {
try managedContext.save()
} catch let error as NSError {
print("could not save. \(error), \(error.userInfo)")
}
print("new single comic crated: title: \(comicToAdd.comicTitle ?? "!! not title !!"), n. \(comicToAdd.issueNumber), owned?: \(comicToAdd.inCollection)")
}
in the main VC I use this to check items in core data
func asyncPrintEntities() {
self.asyncComicEntityArray.removeAll(keepingCapacity: true)
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {return}
let managedContext = appDelegate.persistentContainer.viewContext
let comicFetch : NSFetchRequest<Comic> = Comic.fetchRequest()
asyncFetchRequest = NSAsynchronousFetchRequest<Comic>(fetchRequest: comicFetch) {
[unowned self] (result: NSAsynchronousFetchResult) in
guard let AllComicEntityResult = result.finalResult else {
return
}
self.asyncComicEntityArray = AllComicEntityResult
//************************************
do {
self.asyncComicEntityArray = try managedContext.fetch(comicFetch)
if self.asyncComicEntityArray.count > 0 {
print("Ok! model is not empty!")
} else {
print("No entites availabe")
}
} catch let error as NSError {
print("Fetch error: \(error) description: \(error.userInfo)")
}
guard self.asyncComicEntityArray != nil else {return}
for comicFoundInArray in self.asyncComicEntityArray {
let entity = NSEntityDescription.entity(forEntityName: self.kComicEntityName, in: managedContext)!
var comicTouse = Comic(entity: entity, insertInto: managedContext)
// var comicTouse = Comic() //to be deleted since this kind of init is not allowed, better above insertInto
comicTouse = comicFoundInArray as! Comic
print("comic title: \(comicTouse.comicTitle ?? "error title"), is it in collection? : \(comicTouse.inCollection)")
}
self.MyTableView.reloadData()
//************************************
}
// MARK: - async fetch request 3
do {
try managedContext.execute(asyncFetchRequest)
} catch let error as NSError {
print("Could not fetch \(error), \(error.userInfo)")
}
//end of function
}
In your addingSingleComic you create a new Comic here:
let comicToAdd = Comic(entity: entity, insertInto: managedContext)
Then you assign values to the object's properties.
Separately, in asyncPrintEntities, you also create new Comic objects here:
var comicTouse = Comic(entity: entity, insertInto: managedContext)
This time you do not assign values to the object's properties. They will have no title, etc, because you created them but never assigned a title. This line executes once for every object in asyncComicEntityArray, so if the array has two objects, you create two new objects that contain no data. You don't use comicToUse anywhere except in the one print, but it still exists in the managed object context and will still get saved the next time you save changes.
This is why you're getting extra entries-- because you're creating them in this line of code. It's not clear why you're creating them here. You just executed a fetch request, and then you immediately create a bunch of no-data entries which you don't use. It looks like that entire for loop could just be deleted, because the only thing it does is create these extra entries.
My managedObjectContext hierarchy is as follows: (PSC)<-(writerMOC -- private)<-(mainMOC -- main)<-(backgroundMOC -- private)
I have an NSManagedObject who "name" property is "Banana".
In the backgroundMOC, I get a reference to the object with backgroundMOC.objectWithID, change the NSManagedObject's "name" property to "Apple", and subsequently set it's "syncStatus" property to 1 (flagged for synchronization), then recursively save the moc's with the following routine:
func saveManagedContext(moc: NSManagedObjectContext, shouldSync: Bool = true, completion: (() -> Void)? = nil)
{
print("\nSaving managed object context...")
do {
try moc.save()
if let parentContext = moc.parentContext {
parentContext.performBlock {
self.saveManagedContext(parentContext, shouldSync: shouldSync, completion: completion)
}
}
else {
if shouldSync { SyncEngine.sharedInstance.synchronize(shouldPushUpdates: true) }
completion?()
}
print("Finished saving managed object context...")
} catch {
logger.error("\(error)")
}
}
Once the last moc is saved, a sync routine is called which does its work on the backgroundMOC, which queries the local store for all objects whose syncStatus is 1, again this fetch is called on the backgroundMOC.
let fetchRequest = NSFetchRequest(entityName: entity.name)
let syncPredicate = NSPredicate(format: "%K == %d", JSONKey.SyncStatus.rawValue, 1)
fetchRequest.predicate = syncPredicate
return try backgroundMOC.executeFetchRequest(fetchRequest) as? [SyncableManagedObject] ?? []
This correctly returns the updated object in the array, however, that object's syncStatus property equals 0, and its "name" property is still set to "Banana".
This is really causing me headaches, I felt like i had totally understood how managedObjectContext blocks should work, but this has proven to be quite a puzzle.
UPDATE
Here's the code that prompts the update. This is called from the main thread when the cell is tapped.
func updateNameForCell(cell: UITableViewCell)
{
///gets the object id from the fetchedResultsController
guard let fruitMetaID = tableController.objectIDForCell(cell) else { return }
let backgroundMOC = CoreDataController.sharedInstance.newBackgroundManagedObjectContext()
backgroundMOC.performBlock {
do {
guard let fruit = (backgroundMOC.objectWithID(fruitMetaID) as? FruitMetaData)?.fruit else {
throw //Error
}
print(fruit.name) // "Banana"
fruit.name = "Apple"
fruit.needsSynchronization() //Sets syncStatus to 1
CoreDataController.sharedInstance.saveManagedContext(backgroundMOC)
}
catch {
//handle error
}
}
}
UPDATE AGAIN
Maybe I'm not creating the contexts right. Enlighten me please!
/// The parent to all other NSManagedObjectContexts. Responsible for writting to the store.
lazy var writerManagedObjectContext: NSManagedObjectContext =
{
let managedObjectContext = NSManagedObjectContext(concurrencyType: .PrivateQueueConcurrencyType)
managedObjectContext.performBlockAndWait {
managedObjectContext.persistentStoreCoordinator = self.persistentStoreCoordinator
}
return managedObjectContext
}()
lazy var mainManagedObjectContext: NSManagedObjectContext =
{
let managedObjectContext = NSManagedObjectContext(concurrencyType: .MainQueueConcurrencyType)
managedObjectContext.performBlockAndWait {
managedObjectContext.parentContext = self.writerManagedObjectContext
}
return managedObjectContext
}()
/// The context associated with background syncing..
func newBackgroundManagedObjectContext() -> NSManagedObjectContext
{
let backgroundManagedObjectContext = NSManagedObjectContext(concurrencyType: .PrivateQueueConcurrencyType)
backgroundManagedObjectContext.performBlockAndWait {
backgroundManagedObjectContext.parentContext = self.mainManagedObjectContext
}
return backgroundManagedObjectContext
}
Holding onto child MOCs (children of the main context) is fraught with issues. I would recommend creating a new child (aka backgroundMOC) for each operation that you do.
Without seeing all of your code this looks like an issue with the child context getting out of sync.
Update
Assuming that your creation of the backgroundMOC sets the mainMOC as its parent then I wonder about the -objectWithID: and what it is returning.
I also wonder about your -performBlock: calls. In my head the threading looks fine but better to test. Try changing to -performBlockAndWait: just to test and see if there is a threading race condition. Not a permanent change but eliminates that part of the code as a source of the issue.
Before fetchRequest is called, you should reset context.
backgroundMOC.reset() // add this line
let fetchRequest = NSFetchRequest(entityName: entity.name)
let syncPredicate = NSPredicate(format: "%K == %d", JSONKey.SyncStatus.rawValue, 1)
fetchRequest.predicate = syncPredicate
return try backgroundMOC.executeFetchRequest(fetchRequest) as? [SyncableManagedObject] ?? []
The reason is FruitMetaData is an object(or class) so changing one of its properties/Core Data attributes does not register as a change to the results array ... the object references in the array remain the same.
And NSFetchRequest still returns the same result(by using cache). When use context.reset().This tells the context in the extension to fetch new data every time and ignore the cache.
I've been chasing a bug for a while now and I can't figure it out. I have a class that takes a bunch of parsed data and then calls a method to create new core data "Article" object for each element created from the parsed data. I've shown how I declare the NSManagedObjectContext below.
You will also see the method
Article.createFLOArticleWithStructure(element, inManagedObjectContext: self.articleContext)
I placed this method in an extension to clean up the code. The method is show below.
import Foundation
class FLODataHandler : NSObject, FLOConnectionHandlerDelegate, FLOParserHandlerDelegate, TriathleteParserHandlerDelegate, VeloNewsParserHandlerDelegate, CyclingNewsParserHandlerDelegate, RoadBikeActionParserHandlerDelegate, IronmanParserHandlerDelegate
{
let appDelegate: AppDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
lazy var articleContext: NSManagedObjectContext = self.appDelegate.managedObjectContext!
func floParserHandlerDidFinishParsing(parserHandler : FLOParserHandler)
{
for element in self.floParserHandler!.XMLParsedDataArray!
{
// The pubDate, tilte and link and indicator have been added to the titleLinkArray. I will now add the data to a Core Data Entity
// in the Article+NewsFeedArticle class.
Article.createFLOArticleWithStructure(element, inManagedObjectContext: self.articleContext)
}
}
Extension Code
extension Article
{
class func createFLOArticleWithStructure(articleStructure: DateTitleLink, inManagedObjectContext context: NSManagedObjectContext) -> (Article)
{
// Core data is much simpler in Swift. I have not commented this code since I do not know if it's working yet.
var article = Article()
//var entity = NSEntityDescription("Article", inManagedObjectContext: context)
let fetchRequest = NSFetchRequest(entityName: "Article")
let predicate = NSPredicate(format: "feed == 'FLO Cycling' AND title == %#", articleStructure.title!)
let sortDescriptor = NSSortDescriptor(key: "pubDate", ascending: true)
fetchRequest.sortDescriptors = [sortDescriptor]
// Set up NSError
var fetchError : NSError?
// When you perform a fetch the returned object is an array of the Atricle Entities.
let fetchedObjects = context.executeFetchRequest(fetchRequest, error: &fetchError) as! [Article]
if fetchedObjects.count > 1
{
println("Error! in Article+NewFeedArticle.swift")
}
else if fetchedObjects.count == 0
{
article = NSEntityDescription.insertNewObjectForEntityForName("Article", inManagedObjectContext: context) as! Article
article.feed = "FLO Cycling"
article.pubDate = articleStructure.date!
article.title = articleStructure.title!
article.link = articleStructure.link!
article.theNewArticle = NSNumber(int: 1)
var error : NSError?
if(context.save(&error))
{
println(error!.localizedDescription)
}
}
else if fetchedObjects.count == 1
{
article = fetchedObjects[fetchedObjects.endIndex - 1]
}
return article
}
When I run the code I get stopped on the following line of the extension code and receive the following errors.
article = NSEntityDescription.insertNewObjectForEntityForName("Article", inManagedObjectContext: context) as! Article
CoreData: error: Failed to call designated initializer on
NSManagedObject class 'FLOCycling1_1_1.Article' CoreData: warning:
Unable to load class named 'Article' for entity 'Article'. Class not
found, using default NSManagedObject instead. Could not cast value of
type 'NSManagedObject_Article_' (0x7fe59c3515e0) to
'FLOCycling1_1_1.Article' (0x106139f70).
I've read online about using a prefix in the data model. I've added this to no avail. If you have any idea how I can fix this error I would appreciate the help.
ADDED****
Here is the Article.swift file on request.
import Foundation
import CoreData
#objc class Article: NSManagedObject
{
#NSManaged var feed: String
#NSManaged var link: String
#NSManaged var pubDate: NSDate
#NSManaged var theNewArticle: NSNumber
#NSManaged var title: String
}
Take care,
Jon
The issue had to do with my declaration of Article in this line here.
var article = Article()
In the Swift version calling the line of code above allocates and initializes memory for the Article. In the Objective-C version of my code I called the following.
Article *article = nil;
While I am not sure why, allocating and initializing the Article is the issue. I found this post here about a similar error.
Failed to call designated initializer on NSManagedObject class 'ClassName'
To fix this I changed the code to
var article = Article?()
To be clear, I also changed the Article class to ProjectName.Article.
I hope this helps someone else.
Take care,
Jon
Ok so the problem actually occurs once the code bit var context: NSManagedObjectContext = appDel.managedObjectContext is run I commented it out to confirm that it was that line and it was please note this is my first time learning iOS programming so please try to be as specific as possible in your answer thank you :)
import UIKit
import CoreData
class SecondViewController: UIViewController, UITextFieldDelegate {
#IBOutlet var txtName : UITextField
#IBOutlet var txtDesc : UITextField
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
override func touchesBegan(touches: NSSet!, withEvent event: UIEvent!) {
self.view.endEditing(true)
}
#IBAction func hitAdd(sender : UIButton) {
glTask.newTask(txtName.text, desc: txtDesc.text)
txtName.text = ""
txtDesc.text = ""
self.view.endEditing(true)
self.tabBarController.selectedIndex = 0
var appDel: AppDelegate = (UIApplication.sharedApplication().delegate as AppDelegate)
Right here V
var context: NSManagedObjectContext = appDel.managedObjectContext
This crashes the app once button is pressed ^
The code error message is fatal error Cant unwrap Optional.None
var newTask = NSEntityDescription.insertNewObjectForEntityForName("Tasks", inManagedObjectContext: context) as NSManagedObject
newTask.setValue("test task", forKey: "myTask")
newTask.setValue("test Description", forKey: "myDesc")
context.save(nil)
//println(newTask)
println("Task was saved.")
}
// UITextField Delegate
func textFieldShouldReturn(textField: UITextField!) -> Bool {
textField.resignFirstResponder()
return true
}
}
Looking at the Core Data stack in Swift, managedObjectContext is implemented like this:
var managedObjectContext: NSManagedObjectContext {
if !_managedObjectContext {
let coordinator = self.persistentStoreCoordinator
if coordinator != nil {
_managedObjectContext = NSManagedObjectContext()
_managedObjectContext!.persistentStoreCoordinator = coordinator
}
}
return _managedObjectContext!
}
var _managedObjectContext: NSManagedObjectContext? = nil
As you can see it is backed by an Optional.
The place where this can go wrong is here:
_managedObjectContext = NSManagedObjectContext()
_managedObjectContext!.persistentStoreCoordinator = coordinator
if NSManagedObjectContext() returns a nil, then the backing _managedObjectContext will be nil and you will get this crash at the line where you unwrap it return _managedObjectContext!
To debug this, dig deeper down the stack, its most likely failing to initialize the object model or persistant store, and thus returning nil to you.
Edit:
In the definiton of the getter for var persistentStoreCoordinator: NSPersistentStoreCoordinator
They provide a location (the wall of comments) where you should debug this exact type of issue.
Not sure if OP ever figured this out, but I had a similar issue and realized that the code I copied from another app's AppDelegate was using the project name of that app and that I had forgot to change this line: let modelURL = NSBundle.mainBundle().URLForResource("CoreData", withExtension: "momd") to use "CoreData" instead of the "test" it had from another project.