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

Question

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
}
}

Answer 1

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.

Answer 2

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