NSManagedObjectContext is nil in the UITableViewController class using CoreData - objective-c

Question

i need to display a few elements in a UITableViewController from CoreData, but the NSManagedObjectContext instance, called *managedObjectContext, is nil when the app launching.
This is my UITableViewController.h
#interface TableViewController : UITableViewController
#property(nonatomic,strong) NSArray *listaElementi;
#property (readonly, strong, nonatomic) NSManagedObjectContext *managedObjectContext; //si occupa di gestire come sono strutturate le entity
#end
This is my UITableViewController.m
- (void)viewDidLoad {
[super viewDidLoad];
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription
entityForName:#"Stato" inManagedObjectContext:managedObjectContext];
[fetchRequest setEntity:entity];
NSError *error;
self.listaElementi = [managedObjectContext executeFetchRequest:fetchRequest error:&error];
self.title = #"Stati";
Finally this is my AppDelegate.m
#synthesize managedObjectContext = _managedObjectContext;
#synthesize managedObjectModel = _managedObjectModel;
#synthesize persistentStoreCoordinator = _persistentStoreCoordinator;
- (NSManagedObjectModel *)managedObjectModel {
// The managed object model for the application. It is a fatal error for the application not to be able to find and load its model.
if (_managedObjectModel != nil) {
return _managedObjectModel;
}
NSURL *modelURL = [[NSBundle mainBundle] URLForResource:#"Model" withExtension:#"momd"]; //SETTARE BENE IL MODELLO
_managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
return _managedObjectModel;
}
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
// The persistent store coordinator for the application. This implementation creates and return a coordinator, having added the store for the application to it.
if (_persistentStoreCoordinator != nil) {
return _persistentStoreCoordinator;
}
// Create the coordinator and store
_persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:#"Database.sqlite"];
NSError *error = nil;
NSString *failureReason = #"There was an error creating or loading the application's saved data.";
if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
// Report any error we got.
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
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 _persistentStoreCoordinator;
}
- (NSManagedObjectContext *)managedObjectContext {
// Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.)
if (_managedObjectContext != nil) {
return _managedObjectContext;
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (!coordinator) {
return nil;
}
_managedObjectContext = [[NSManagedObjectContext alloc] init];
[_managedObjectContext setPersistentStoreCoordinator:coordinator];
return _managedObjectContext;
}
Could you help me? When I created the project I don't checked the adding core data box , but I implemented all manually and I just created the model and I just Inserted a few element into the Database, is a possible cause of the problem?

Answer 1

Try this in viewDidLoad
- (void)viewDidLoad {
[super viewDidLoad];
AppDelegate *delgate = (AppDelegate *)[[UIApplication
sharedApplication]delegate];
self.managedObjectContext = delegate.managedObjectContext;
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription
entityForName:#"Stato" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
NSError *error;
self.listaElementi = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];
}