title: Core Data error when fetching
body: <p>I am new to Core Data and I have been trying to fetch the entities that I have created but I keep getting error messages thrown at me. </p>
  
  <p>The error is as follows:</p>
  
  <pre><code>CoreData: error: -addPersistentStoreWithType:SQLite configuration:(null) URL:file:///var/mobile/Containers/Data/Application/4A0BBC17-674F-4A5D-80F7-72174D71B95F/Documents/Todogorithm.sqlite options:(null) ... returned error Error Domain=NSCocoaErrorDomain Code=134100 "The managed object model version used to open the persistent store is incompatible with the one that was used to create the persistent store." UserInfo={metadata={
      NSPersistenceFrameworkVersion = 641;
      NSStoreModelVersionHashes =     {
          Task = &lt;3db44fe3 d21215ef eee9476a ae204647 b49829de 00b4784c 7715b5ff a252dcab&gt;;
      };
      NSStoreModelVersionHashesVersion = 3;
      NSStoreModelVersionIdentifiers =     (
          ""
      );
      NSStoreType = SQLite;
      NSStoreUUID = "DFB8723E-7D5B-44A0-AFB9-E9E0F7E39E85";
      "_NSAutoVacuumLevel" = 2;
  }, reason=The model used to open the store is incompatible with the one used to create the store} with userInfo dictionary {
      metadata =     {
          NSPersistenceFrameworkVersion = 641;
          NSStoreModelVersionHashes =         {
              Task = &lt;3db44fe3 d21215ef eee9476a ae204647 b49829de 00b4784c 7715b5ff a252dcab&gt;;
          };
          NSStoreModelVersionHashesVersion = 3;
          NSStoreModelVersionIdentifiers =         (
              ""
          );
          NSStoreType = SQLite;
          NSStoreUUID = "DFB8723E-7D5B-44A0-AFB9-E9E0F7E39E85";
          "_NSAutoVacuumLevel" = 2;
      };
      reason = "The model used to open the store is incompatible with the one used to create the store";
  }
  </code></pre>
  
  <p>The error is thrown when the <code>viewDidAppear</code> on my view controller is called. Here is my <code>viewDidAppear</code>:
      [super viewDidAppear:animated];</p>
  
  <pre><code>AppDelegate *appDelegate = [[AppDelegate alloc] init];
  
  NSManagedObjectContext *context = [appDelegate managedObjectContext];
  
  NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:@"Task"];
  _results = [context executeFetchRequest:request error:nil];
  </code></pre>
  
  <p>The code there calls the <code>managedObjectContext</code> in my appDelegate, and in that method the <code>persistentStoreCoordinator</code> method is called (this is where the error is actually thrown). The two methods from AppDelegate.m are below:</p>
  
  <pre><code>- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
      // The persistent store coordinator for the application. This implementation creates and returns 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:@"Todogorithm.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:&amp;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] initWithConcurrencyType:NSMainQueueConcurrencyType];
      [_managedObjectContext setPersistentStoreCoordinator:coordinator];
  </code></pre>
  
  <p><strong>Any ideas as to why the error in <code>persistentStoreCoordinator</code> is being called?</strong></p>