ios could not locate NSManagedObjectModel , NSInternalConsistencyException - ios

Question

I know similar questions have been asked but they all have different answers and none seem to help me.
So, I've got an app called TherapistScheduler, which has therapistScheduler.xcdatamodel in a /Data folder at the root of the project. Inside that folder is a Session.h and Session.m file, which match up with my Session entity in my data model.
My app delegate has the functions managedObjectContext, managedObjectModel, and persistantStoreCoodinator in it.
Inside my applicationDidFinishLaunching method, I've added a view controller (loginViewController) over the top of my rootViewController (which is a tabBarController), and I'm trying to access my Session entity from there.
I'm using the following code to try and save a value - this is throwing the error:
// create session
Session *session = (Session *) [NSEntityDescription insertNewObjectForEntityForName:#"Session" inManagedObjectContext:self.managedObjectContext];
[session setSessionHash:strUserhash];
The loginViewController.h file contains:
NSManagedObjectContext *managedObjectContext; // in the interface declaration
#property (nonatomic, retain) NSManagedObjectContext *managedObjectContext; // after the interface
The loginViewController.m file contains
#synthesize managedObjectContext;
Do I need to do something in the loginViewController viewDidLoad to initialise the managedObjectContext? I'm a bit lost as to how this all works. I want to be able to access the data stored in the managedObjectContext from any view I switch to on the tab bar.
I know I'll probably need to add more code to the question, but I don't know what else is needed.
The error I'm getting is this:
TherapistScheduler[40752:207] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '+entityForName: could not locate an NSManagedObjectModel for entity name 'Session''
*** Call stack at first throw:
(
0 CoreFoundation 0x02581919 __exceptionPreprocess + 185
1 libobjc.A.dylib 0x0295b5de objc_exception_throw + 47
2 CoreData 0x0004525b +[NSEntityDescription entityForName:inManagedObjectContext:] + 187
3 CoreData 0x0007cd8b +[NSEntityDescription insertNewObjectForEntityForName:inManagedObjectContext:] + 59
4 TherapistScheduler 0x000030ce -[LoginViewController processLoginForUserhash:andType:] + 142
5 TherapistScheduler 0x000039fa -[LoginViewController connectionDidFinishLoading:] + 330
6 Foundation 0x01f91666 -[NSURLConnection(NSURLConnectionReallyInternal) sendDidFinishLoading] + 108
7 Foundation 0x01f915bf _NSURLConnectionDidFinishLoading + 133
8 CFNetwork 0x02b8d9f1 _ZN19URLConnectionClient23_clientDidFinishLoadingEPNS_26ClientConnectionEventQueueE + 285
9 CFNetwork 0x02c56c72 _ZN19URLConnectionClient26ClientConnectionEventQueue33processAllEventsAndConsumePayloadEP20XConnectionEventInfoI12XClientEvent18XClientEventParamsEl + 402
10 CFNetwork 0x02c570ea _ZN19URLConnectionClient26ClientConnectionEventQueue33processAllEventsAndConsumePayloadEP20XConnectionEventInfoI12XClientEvent18XClientEventParamsEl + 1546
11 CFNetwork 0x02c570ea _ZN19URLConnectionClient26ClientConnectionEventQueue33processAllEventsAndConsumePayloadEP20XConnectionEventInfoI12XClientEvent18XClientEventParamsEl + 1546
12 CFNetwork 0x02b82dfe _ZN19URLConnectionClient13processEventsEv + 100
13 CFNetwork 0x02b82c95 _ZN17MultiplexerSource7performEv + 247
14 CoreFoundation 0x02562d7f __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 15
15 CoreFoundation 0x024c11dd __CFRunLoopDoSources0 + 333
16 CoreFoundation 0x024c07c6 __CFRunLoopRun + 470
17 CoreFoundation 0x024c0280 CFRunLoopRunSpecific + 208
18 CoreFoundation 0x024c01a1 CFRunLoopRunInMode + 97
19 GraphicsServices 0x02de62c8 GSEventRunModal + 217
20 GraphicsServices 0x02de638d GSEventRun + 115
21 UIKit 0x00215b58 UIApplicationMain + 1160
22 TherapistScheduler 0x00001f3d main + 125
23 TherapistScheduler 0x00001eb5 start + 53
24 ??? 0x00000001 0x0 + 1
)
terminate called after throwing an instance of 'NSException'

Answer 1

I had to refer to the managedObjectContext as a property of the app delegate not self. So it looked like appDelegate.managedObjectContext.

Answer 2

When you passed the managedObjectContext, I think what you did is like this:
TimelineTableViewController * timelineTableViewController;
timelineTableViewController = [TimelineTableViewController alloc];
[timelineTableViewController initWithStyle:UITableViewStylePlain];
timelineTableViewController.managedObjectContext = self.managedObjectContext;
//...
and then in TimelineTableViewController's viewDidLoad: method, you wanted to fetch the data by managedObjectContext, huh?
I debugged this issue and found that TimelineTableViewController's viewDidLoad: will be dispatched quicker than timelineTableViewController.managedObjectContext = self.managedObjectContext; (where you passed the managedObjectContext from parent (or the AppDelegate) to child). So when you were trying to fetch the data, the managedObjectContext is nil actually. That's why you got this issue:
'+entityForName: could not locate an NSManagedObjectModel for entity name 'Session''
WORKAROUND:
What you have to do is to make sure that the managedObjectContext is not nil when you need to fetch the data:
TimelineTableViewController * timelineTableViewController;
timelineTableViewController = [TimelineTableViewController alloc];
timelineTableViewController.managedObjectContext = self.managedObjectContext;
[timelineTableViewController initWithStyle:UITableViewStylePlain];
// ...
I just solved this issue by this way (no need to use AppDelegate's managedObjectContext directly).