Error: "'NSManagedObjectContext' is not convertible to 'UInt8'" - iphone

This is the core data tutorial that I am trying to complete. The error is in the saveContext() function.
import UIKit
import CoreData
#UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
// ...
func saveContext () {
var error: NSError? = nil
// There second line below this comment is providing for the error referenced in the question title.
let managedObjectContext = self.managedObjectContext
if (managedObjectContext != nil)
{
if managedObjectContext.hasChanges && !managedObjectContext.save(&error) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
//println("Unresolved error \(error), \(error.userInfo)")
abort()
}
}
}
// #pragma mark - Core Data stack
// Returns the managed object context for the application.
// If the context doesn't already exist, it is created and bound to the persistent store coordinator for the application.
var managedObjectContext: NSManagedObjectContext {
if !(_managedObjectContext != nil) {
let coordinator = self.persistentStoreCoordinator
if (coordinator != nil) {
_managedObjectContext = NSManagedObjectContext()
_managedObjectContext!.persistentStoreCoordinator = coordinator
}
}
return _managedObjectContext!
}
var _managedObjectContext: NSManagedObjectContext? = nil
// Returns the managed object model for the application.
// If the model doesn't already exist, it is created from the application's model.
var managedObjectModel: NSManagedObjectModel {
if (_managedObjectModel != nil) {
let modelURL = NSBundle.mainBundle().URLForResource("ContactU", withExtension: "momd")
_managedObjectModel = NSManagedObjectModel(contentsOfURL: modelURL!)
}
return _managedObjectModel!
}
var _managedObjectModel: NSManagedObjectModel? = nil
// Returns the persistent store coordinator for the application.
// If the coordinator doesn't already exist, it is created and the application's store added to it.
var persistentStoreCoordinator: NSPersistentStoreCoordinator {
if !(_persistentStoreCoordinator != nil) {
let storeURL = self.applicationDocumentsDirectory.URLByAppendingPathComponent("ContactU.sqlite")
var error: NSError? = nil
_persistentStoreCoordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
if _persistentStoreCoordinator!.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: storeURL, options: nil, error: &error) == nil {
/*
Replace this implementation with code to handle the error appropriately.
abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
Typical reasons for an error here include:
* The persistent store is not accessible;
* The schema for the persistent store is incompatible with current managed object model.
Check the error message to determine what the actual problem was.
If the persistent store is not accessible, there is typically something wrong with the file path. Often, a file URL is pointing into the application's resources directory instead of a writeable directory.
If you encounter schema incompatibility errors during development, you can reduce their frequency by:
* Simply deleting the existing store:
NSFileManager.defaultManager().removeItemAtURL(storeURL, error: nil)
* Performing automatic lightweight migration by passing the following dictionary as the options parameter:
[NSMigratePersistentStoresAutomaticallyOption: true, NSInferMappingModelAutomaticallyOption: true]
Lightweight migration will only work for a limited set of schema changes; consult "Core Data Model Versioning and Data Migration Programming Guide" for details.
*/
//println("Unresolved error \(error), \(error!.userInfo)")
abort()
}
}
return _persistentStoreCoordinator!
}
var _persistentStoreCoordinator: NSPersistentStoreCoordinator? = nil
// #pragma mark - Application's Documents directory
// Returns the URL to the application's Documents directory.
var applicationDocumentsDirectory: NSURL {
let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
return urls[urls.count-1] as NSURL
}
}

In saveContext() your constant managedObjectContext is of type NSManagedObjectContext, yet in the next line you are testing it against nil, which is never possible. Only an optional type (e.g. NSManagedObjectContext?) can be nil. See "Optionals" in The Swift Programming Language: The Basics for more info.
This could be the reason for your error, although it is unclear from the code and error exactly what it is being referred to. Swift's compiler errors aren't all fantastically helpful at this early stage in the development of the language, and so they sometimes need to be taken with a pinch of salt.

I can't give you an answer for sure however you can try this saveContext() way
lazy var managedObjectContext: NSManagedObjectContext? =
{
// Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.) This property is optional since there are legitimate error conditions that could cause the creation of the context to fail.
let coordinator = self.persistentStoreCoordinator
if coordinator == nil
{
return nil
}
var managedObjectContext = NSManagedObjectContext()
managedObjectContext.persistentStoreCoordinator = coordinator
return managedObjectContext
}()
func saveContext ()
{
if let moc = self.managedObjectContext
{
var error: NSError? = nil
if moc.hasChanges && !moc.save(&error) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog("Unresolved error \(error), \(error!.userInfo)")
abort()
}
}
}
Besides if you want to pure-swift you shouldn't use "#pragma", Just use // MARK:: - Your tag here

Related

Core Data, Initialize managedObjectContext

I'm trying to learn how to use Core Date to store images for an app I'm working on. I've created an entity and imported Core Data. On all the tutorials I've watched thus far, they create a var that contains.
let moc = (UIApplication.sharedApplication().delegate as! AppDelegate).managedObjectContext
For some reason, when I put that line into my project, I get an error:
Value of type AppDelegate has no member managedObjectContext
It seems like that the tutorials you read all checks the "Use Core Data" checkbox when creating a project:
If you checked this checkbox, you would have had a property called managedObjectContext declared in AppDelegate.
But since you didn't check the checkbox, it's not generated for you.
Here is the extra code that will be generated:
// MARK: - Core Data stack
lazy var applicationDocumentsDirectory: NSURL = {
// The directory the application uses to store the Core Data store file. This code uses a directory named "com.TimerReminder" in the application's documents Application Support directory.
let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
return urls[urls.count-1]
}()
lazy var managedObjectModel: NSManagedObjectModel = {
// The managed object model for the application. This property is not optional. It is a fatal error for the application not to be able to find and load its model.
let modelURL = NSBundle.mainBundle().URLForResource("XXX", withExtension: "momd")!
return NSManagedObjectModel(contentsOfURL: modelURL)!
}()
lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator = {
// The persistent store coordinator for the application. This implementation creates and returns a coordinator, having added the store for the application to it. This property is optional since there are legitimate error conditions that could cause the creation of the store to fail.
// Create the coordinator and store
let coordinator = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent("SingleViewCoreData.sqlite")
var failureReason = "There was an error creating or loading the application's saved data."
do {
try coordinator.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: nil)
} catch {
// Report any error we got.
var dict = [String: AnyObject]()
dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data"
dict[NSLocalizedFailureReasonErrorKey] = failureReason
dict[NSUnderlyingErrorKey] = error as NSError
let wrappedError = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
// Replace this with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog("Unresolved error \(wrappedError), \(wrappedError.userInfo)")
abort()
}
return coordinator
}()
lazy var managedObjectContext: NSManagedObjectContext = {
// Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.) This property is optional since there are legitimate error conditions that could cause the creation of the context to fail.
let coordinator = self.persistentStoreCoordinator
var managedObjectContext = NSManagedObjectContext(concurrencyType: .MainQueueConcurrencyType)
managedObjectContext.persistentStoreCoordinator = coordinator
return managedObjectContext
}()
// MARK: - Core Data Saving support
func saveContext () {
if managedObjectContext.hasChanges {
do {
try managedObjectContext.save()
} catch {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
let nserror = error as NSError
NSLog("Unresolved error \(nserror), \(nserror.userInfo)")
abort()
}
}
}
Just copy the above code and add to your app delegate file. Note that you should replace the "XXX" in this line:
let modelURL = NSBundle.mainBundle()
.URLForResource("XXX", withExtension: "momd")!
with the name of your project.
Also, the checkbox also makes Xcode generate a call to saveContext in the applicationWillTerminate method:
func applicationWillTerminate(application: UIApplication) {
// Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
// Saves changes in the application's managed object context before the application terminates.
self.saveContext()
}

Swift Core Data NSFetchRequest no results

I've encountered a problem when working with Core Data. I have this Core Data Model named 'Test.xcdatamodeld' and it contains only one entity named 'Data'. This Data entity contains one attribute named 'currCount' of type Int32.
What I'm trying to do is to read the value of 'currCount' but when I try to fetch something out of my entity 'Data' there are no results.
This is my fetching code:
var appDel:AppDelegate = (UIApplication.sharedApplication().delegate as AppDelegate)
var context:NSManagedObjectContext = appDel.managedObjectContext!
var request = NSFetchRequest(entityName: "Data")
request.returnsObjectsAsFaults = false
var results: NSArray = context.executeFetchRequest(request, error: nil)!
var currCount:Int32 = 0
if results.count > 0 {
var res = results[0] as NSManagedObject
currCount = Int32(res.valueForKey("currCount") as Int)
println("Local Count: \(currCount)")
return currCount
}
else {
println("firstTime no Questions")
return 0
}
I always end up in the else-statement. I don't understand what I'm doing wrong. I've been going this way in another project and it works fine.
My AppDelegate.swift is as follows:
import UIKit
import CoreData
#UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
var window: UIWindow?
func application(application: UIApplication!, didFinishLaunchingWithOptions launchOptions: NSDictionary!) -> Bool {
return true
}
func applicationWillResignActive(application: UIApplication!) {
// Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
// Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
}
func applicationDidEnterBackground(application: UIApplication!) {
// Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
// If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
}
func applicationWillEnterForeground(application: UIApplication!) {
// Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
}
func applicationDidBecomeActive(application: UIApplication!) {
// Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}
func applicationWillTerminate(application: UIApplication!) {
// Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
}
// MARK: - Core Data stack
lazy var applicationDocumentsDirectory: NSURL = {
// The directory the application uses to store the Core Data store file. This code uses a directory named "com.jqsoftware.MyLog" in the application's documents Application Support directory.
let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
return urls[urls.count-1] as NSURL
}()
lazy var managedObjectModel: NSManagedObjectModel = {
// The managed object model for the application. This property is not optional. It is a fatal error for the application not to be able to find and load its model.
let modelURL = NSBundle.mainBundle().URLForResource("Test", withExtension: "momd")!
return NSManagedObjectModel(contentsOfURL: modelURL)!
}()
lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator? = {
// The persistent store coordinator for the application. This implementation creates and return a coordinator, having added the store for the application to it. This property is optional since there are legitimate error conditions that could cause the creation of the store to fail.
// Create the coordinator and store
var coordinator: NSPersistentStoreCoordinator? = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent("Test.sqlite")
var error: NSError? = nil
var failureReason = "There was an error creating or loading the application's saved data."
if coordinator!.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: nil, error: &error) == nil {
coordinator = nil
// Report any error we got.
var dict = [String: AnyObject]()
dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data"
dict[NSLocalizedFailureReasonErrorKey] = failureReason
dict[NSUnderlyingErrorKey] = error
error = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
// Replace this with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog("Unresolved error \(error), \(error!.userInfo)")
abort()
}
return coordinator
}()
lazy var managedObjectContext: NSManagedObjectContext? = {
// Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.) This property is optional since there are legitimate error conditions that could cause the creation of the context to fail.
let coordinator = self.persistentStoreCoordinator
if coordinator == nil {
return nil
}
var managedObjectContext = NSManagedObjectContext()
managedObjectContext.persistentStoreCoordinator = coordinator
return managedObjectContext
}()
// MARK: - Core Data Saving support
func saveContext () {
if let moc = self.managedObjectContext {
var error: NSError? = nil
if moc.hasChanges && !moc.save(&error) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog("Unresolved error \(error), \(error!.userInfo)")
abort()
}
}
}
}
EDIT
Even if I save something to currCount before fetching it again, I get 0 results. This is the code I use for saving (which comes before the code above):
var appDel:AppDelegate = (UIApplication.sharedApplication().delegate as AppDelegate)
var context:NSManagedObjectContext = appDel.managedObjectContext!
var request = NSFetchRequest(entityName: "Data")
request.returnsObjectsAsFaults = false
var results: NSArray = context.executeFetchRequest(request, error: nil)!
var currentCount:Int32 = 5
var newCount = NSEntityDescription.insertNewObjectForEntityForName("Data", inManagedObjectContext: context) as NSManagedObject
newHp.setValue(currentCount, forKey: "currCount")
Once you have inserted something on your context, you should save it to make changes permanent (I suppose you are using a SQLite store).
In other words, you need to run a context.save(&error) method.
Update 1
var error: NSError?
if !context.save(&error) {
println("Error saving context: \(error?.localizedDescription)\n\(error?.userInfo)")
}

Could not save data in core data

I am new to core data , in order to add data
in xcode 6.1.1 using swift
this button function should take username and password from two text fields and save them
#IBAction func save(sender: AnyObject) {
var appDel: AppDelegate = (UIApplication.sharedApplication().delegate as AppDelegate)
var context: NSManagedObjectContext = appDel.managedObjectContext!
var newUser = NSEntityDescription.insertNewObjectForEntityForName("Users", inManagedObjectContext: context) as NSManagedObject
newUser.setValue(""+username.text, forKey: "username")
newUser.setValue(password.text, forKey: "password")
context.save(nil)
println(newUser)
println("Object Saved")
}
this code compile, how ever it has a run time error
ones I click on it I see this error
2015-01-26 21:40:55.160 cordatafirst[2104:1324567] CoreData: error: -addPersistentStoreWithType:SQLite configuration:(null)
MY AppDelegate.swift file
//
// AppDelegate.swift
// cordatafirst
//
// Created by Mustafa on 1/26/15.
// Copyright (c) 2015 Rashwan. All rights reserved.
//
import UIKit
import CoreData
#UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
var window: UIWindow?
func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
// Override point for customization after application launch.
return true
}
func applicationWillResignActive(application: UIApplication) {
// Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
// Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
}
func applicationDidEnterBackground(application: UIApplication) {
// Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
// If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
}
func applicationWillEnterForeground(application: UIApplication) {
// Called as part of the transition from the background to the inactive state; here you can undo many of the changes made on entering the background.
}
func applicationDidBecomeActive(application: UIApplication) {
// Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}
func applicationWillTerminate(application: UIApplication) {
// Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.
// Saves changes in the application's managed object context before the application terminates.
self.saveContext()
}
// MARK: - Core Data stack
lazy var applicationDocumentsDirectory: NSURL = {
// The directory the application uses to store the Core Data store file. This code uses a directory named "edu.self.cordatafirst" in the application's documents Application Support directory.
let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
return urls[urls.count-1] as NSURL
}()
lazy var managedObjectModel: NSManagedObjectModel = {
// The managed object model for the application. This property is not optional. It is a fatal error for the application not to be able to find and load its model.
let modelURL = NSBundle.mainBundle().URLForResource("cordatafirst", withExtension: "momd")!
return NSManagedObjectModel(contentsOfURL: modelURL)!
}()
lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator? = {
// The persistent store coordinator for the application. This implementation creates and return a coordinator, having added the store for the application to it. This property is optional since there are legitimate error conditions that could cause the creation of the store to fail.
// Create the coordinator and store
var coordinator: NSPersistentStoreCoordinator? = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent("cordatafirst.sqlite")
var error: NSError? = nil
var failureReason = "There was an error creating or loading the application's saved data."
if coordinator!.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: nil, error: &error) == nil {
coordinator = nil
// Report any error we got.
let dict = NSMutableDictionary()
dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data"
dict[NSLocalizedFailureReasonErrorKey] = failureReason
dict[NSUnderlyingErrorKey] = error
error = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
// Replace this with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog("Unresolved error \(error), \(error!.userInfo)")
abort()
}
return coordinator
}()
lazy var managedObjectContext: NSManagedObjectContext? = {
// Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.) This property is optional since there are legitimate error conditions that could cause the creation of the context to fail.
let coordinator = self.persistentStoreCoordinator
if coordinator == nil {
return nil
}
var managedObjectContext = NSManagedObjectContext()
managedObjectContext.persistentStoreCoordinator = coordinator
return managedObjectContext
}()
// MARK: - Core Data Saving support
func saveContext () {
if let moc = self.managedObjectContext {
var error: NSError? = nil
if moc.hasChanges && !moc.save(&error) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog("Unresolved error \(error), \(error!.userInfo)")
abort()
}
}
}
}
thanks in advance
It seems like your persistent store is not added. Does your AppDelegate look like THIS ? (I've got this file from THIS tutorial, but it's essentially the same among most apps)

Swift: Updated and got error: "cannot invoke '!=' with argument list of type.."

Everything was fine in Xcode beta 5 but now in full fledged Xcode I'm getting 2 similar errors in my App Delegate:
"cannot invoke '!=' with argument list of type '(NSManagedObjectContext, NilLiteralConvertible')"
"cannot invoke '!=' with argument list of type '(NSPersistentStoreCoordinator, NilLiteralConvertible')"
I tried replacing the != with !== and I get a different error. I don't see what the problem is with !=.
The code:
func saveContext () {
var error: NSError? = nil
let managedObjectContext = self.managedObjectContext
if managedObjectContext != nil { //THIS LINE
if managedObjectContext.hasChanges && !managedObjectContext.save(&error) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate.
//println("Unresolved error \(error), \(error.userInfo)")
abort()
}
}
}
// #pragma mark - Core Data stack
// Returns the managed object context for the application.
// If the context doesn't already exist, it is created and bound to the persistent store coordinator for the application.
var managedObjectContext: NSManagedObjectContext {
if _managedObjectContext !== nil {
let coordinator = self.persistentStoreCoordinator
if coordinator != nil { //THIS LINE
_managedObjectContext = NSManagedObjectContext()
_managedObjectContext!.persistentStoreCoordinator = coordinator
}
}
return _managedObjectContext!
}
var _managedObjectContext: NSManagedObjectContext? = nil
I have a new error: "'NSManagedObjectContext?' does not have a member named 'hasChanges'"
In this code:
func saveContext () {
var error: NSError? = nil
let managedObjectContext = self.managedObjectContext
if managedObjectContext != nil {
if managedObjectContext.hasChanges && !managedObjectContext.save(&error) { //This line
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate.
//println("Unresolved error \(error), \(error.userInfo)")
abort()
}
}
}
The reason for this is because NSManagedObjectContext, and probably NSPersistentStoreCoordinator, do not conform to the Equatable protocol. In order to use == and !=, an object needs to conform to this protocol.
=== and !== do not check equality in that sense. These check to see if two objects are in fact the *same object`. Not with similar values. They both point to the same object in memory.
You are able to check this on the two noted types because they are objects. This should work fine for your situation.
About your second issue, your code should look like this:
func saveContext () {
var error: NSError? = nil
let managedObjectContext = self.managedObjectContext
if let moc = managedObjectContext {
if moc.hasChanges && !moc.save(&error) { //This line
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate.
//println("Unresolved error \(error), \(error.userInfo)")
abort()
}
}
}
The difference here is if let moc = managedObjectContext: if managedObjectContext is not nil, the value is stored in the constant moc. Otherwise, whatever is inside does not get executed. You can read more about optionals here.
self.managedObjectContext is here typed as an NSManagedObjectContext, not an NSManagedObjectContext?.
You can't compare a var to nil unless it's of type Optional<>, implements Equatable, or is nil itself.

Swift : Cannot assign to "" in self

In Swift, I have a computed property called managedObjectContext: NSManagedObjectContext. when I try to initialise it like:
var managedObjectContext: NSManagedObjectContext? {
get {
createManagedObjectContext()
return self.managedObjectContext
}
set(newManagedObjectContext) {
self.manageObjectContext = newManagedObjectContext
}
}
func createManagedObjectContext() -> NSManagedObjectContext {
if let coordinator = persistentStorageCoordinator() as NSPersistentStoreCoordinator!
{
self.managedObjectContext = NSManagedObjectContext()
self.managedObjectContext!.persistentStoreCoordinator = coordinator
NSNotificationCenter.defaultCenter().addObserver(self, selector: "handleBackgroundMOCDidSaveNotification:", name: NSManagedObjectContextDidSaveNotification, object: self.managedObjectContext)
}
return self.managedObjectContext!;
}
I am getting an error saying : Cannot assign to "managedObjectContext" in self.
Can anybody help to fix this?
Thanks in advance.
You also receive this compile error when you're trying to assign a value to a let constant. Changing the variable's type to var should solve it, in this case.
A lazy stored property (see the Swift Programming Language book, page 313) is more appropriate for what you are trying to do here.
lazy var managedObjectContext = createManagedObjectContext()
createManagedObjectContext() won't be called until you attempt to access the property the first time (and only the first time).
Your problem is that you are using a computed property as if it were a standard property, you are effectively attempting to call the setter recursively . You don't need to use a computed property here, just a standard property -
var managedObjectContext: NSManagedObjectContext?
A computed property is one whose value is computed when required based on other properties - For example the "center" property in the Swift Programming Language -
var center: Point {
get {
let centerX = origin.x + (size.width / 2)
let centerY = origin.y + (size.height / 2)
return Point(x: centerX, y: centerY)
}
set(newCenter) {
origin.x = newCenter.x - (size.width / 2)
origin.y = newCenter.y - (size.height / 2)
}
}
Excerpt From: Apple Inc. “The Swift Programming Language.” iBooks. https://itunes.apple.com/au/book/swift-programming-language/id881256329?mt=11
Center is determined by the origin and size, and setting the center affects the origin
Add it!! = )
// MARK: - Core Data stack
lazy var applicationDocumentsDirectory: NSURL = {
// The directory the application uses to store the Core Data store file. This code uses a directory named "com.YOURNAME_OTHERS.YOURAPP" in the application's documents Application Support directory.
let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
return urls[urls.count-1] as NSURL
}()
lazy var managedObjectModel: NSManagedObjectModel = {
// The managed object model for the application. This property is not optional. It is a fatal error for the application not to be able to find and load its model.
let modelURL = NSBundle.mainBundle().URLForResource("YOURAPP", withExtension: "momd")
return NSManagedObjectModel(contentsOfURL: modelURL)
}()
lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator? = {
// The persistent store coordinator for the application. This implementation creates and return a coordinator, having added the store for the application to it. This property is optional since there are legitimate error conditions that could cause the creation of the store to fail.
// Create the coordinator and store
var coordinator: NSPersistentStoreCoordinator? = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)
let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent("YOURAPP.sqlite")
var error: NSError? = nil
var failureReason = "There was an error creating or loading the application's saved data."
if coordinator!.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: nil, error: &error) == nil {
coordinator = nil
// Report any error we got.
let dict = NSMutableDictionary()
dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data"
dict[NSLocalizedFailureReasonErrorKey] = failureReason
dict[NSUnderlyingErrorKey] = error
error = NSError.errorWithDomain("YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)
// Replace this with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog("Unresolved error \(error), \(error!.userInfo)")
abort()
}
return coordinator
}()
lazy var managedObjectContext: NSManagedObjectContext? = {
// Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.) This property is optional since there are legitimate error conditions that could cause the creation of the context to fail.
let coordinator = self.persistentStoreCoordinator
if coordinator == nil {
return nil
}
var managedObjectContext = NSManagedObjectContext()
managedObjectContext.persistentStoreCoordinator = coordinator
return managedObjectContext
}()
// MARK: - Core Data Saving support
func saveContext () {
if let moc = self.managedObjectContext {
var error: NSError? = nil
if moc.hasChanges && !moc.save(&error) {
// Replace this implementation with code to handle the error appropriately.
// abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
NSLog("Unresolved error \(error), \(error!.userInfo)")
//abort()
}
}
}