title: Problem with entityForName & ManagedObjectContext when extending tutorial material
body: <p>Afternoon all,</p>
  
  <p>I tried to add a second data entity to the persistent store in the (locations) coredata tutorial code, and then access this in a new view. I think that I've followed the tutorial, and checked that I'm doing a clean build etc, but can't see what to change to prevent it crashing.</p>
  
  <p>I'm afraid I'm at my wits end with this one, and can't seem to find the step that I've missed. I've pasted the header and code files below, please let me know if I need to share any more of the code. The crash seems to happen on the line:</p>
  
  <pre><code>NSEntityDescription *entity = [NSEntityDescription entityForName:@"Album" inManagedObjectContext:[self managedObjectContext]];
  </code></pre>
  
  <p>There is one other line in the code that refers to galleryviewcontroller at the moment, and that's in the main application delegate:</p>
  
  <pre><code>galleryViewController.managedObjectContext = [self managedObjectContext];
  </code></pre>
  
  <p>GalleryViewController.h</p>
  
  <pre><code>#import &lt;UIKit/UIKit.h&gt;
  
  
  @interface GalleryViewController : UIViewController {
     NSManagedObjectContext *managedObjectContext;        
     int rowNumber;
     IBOutlet UILabel *lblMessage;
     UIBarButtonItem *addButton;
     NSMutableArray *imagesArray;
  }
  
  @property (readwrite) int rowNumber;
  @property (nonatomic,retain) UILabel *lblMessage;
  @property (nonatomic,retain) NSMutableArray *imagesArray;
  @property (nonatomic, retain) NSManagedObjectContext *managedObjectContext; 
  
  @property (nonatomic, retain) UIBarButtonItem *addButton;
  
  -(void)updateRowNumber:(int)theIndex;
  -(void)addImage;
  
  @end
  </code></pre>
  
  <p>GalleryViewController.m</p>
  
  <pre><code>#import "RootViewController.h"
  #import "LocationsAppDelegate.h"
  #import "Album.h"
  #import "GalleryViewController.h"
  #import "Image.h"
  
  
  @implementation GalleryViewController
  
  @synthesize lblMessage,rowNumber,addButton,managedObjectContext;
  @synthesize imagesArray;
  
  /*
   // The designated initializer.  Override if you create the controller programmatically and want to perform customization that is not appropriate for viewDidLoad.
  - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
      if ((self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil])) {
          // Custom initialization
      }
      return self;
  }
  */
  -(void)updateRowNumber:(int)theIndex{
      rowNumber=theIndex;
      LocationsAppDelegate *mainDelegate =(LocationsAppDelegate *)[[UIApplication sharedApplication] delegate];   
      Album *anAlbum = [mainDelegate.albumsArray objectAtIndex:rowNumber];      
      lblMessage.text = anAlbum.uniqueAlbumIdentifier;
  }
  
  
  
  // Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
  - (void)viewDidLoad {
      [super viewDidLoad];    
      addButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(addImage)];
      addButton.enabled = YES;
      self.navigationItem.rightBarButtonItem = addButton;
  
      /* Found this in another answer, adding it to the code didn't help.
      if (managedObjectContext == nil) {
          managedObjectContext = [[[UIApplication sharedApplication] delegate] managedObjectContext];
      }
     */ 
  
      NSFetchRequest *request = [[NSFetchRequest alloc] init];
      NSEntityDescription *entity = [NSEntityDescription entityForName:@"Album" inManagedObjectContext:[self managedObjectContext]];
      [request setEntity:entity];
  
      // Order the albums by creation date, most recent first.
      NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"imagePath" ascending:NO];
      NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
      [request setSortDescriptors:sortDescriptors];
      [sortDescriptor release];
      [sortDescriptors release];
  
      // Execute the fetch -- create a mutable copy of the result.
      NSError *error = nil;
      NSMutableArray *mutableFetchResults = [[managedObjectContext executeFetchRequest:request error:&amp;error] mutableCopy];
      if (mutableFetchResults == nil) {
          // Handle the error.
      }
  
      [self setImagesArray:mutableFetchResults];
  
      int a = 5;
      int b = 10;
  
      for( int i=0; i&lt;[imagesArray count]; i++ )
      {
          if( a == 325 )
          {
              a = 5;
              b += 70;
          }
          UIImageView *any = [[UIImageView alloc] initWithFrame:CGRectMake(a,b,70,60)];
          any.image = [imagesArray objectAtIndex:i];
          any.tag = i;
          [self.view addSubview:any];
          [any release];
          a += 80;
      }
  
  }       
  -(void)addImage{
      NSString *msg = [NSString stringWithFormat:@"%i",rowNumber];
      UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Add image to" message:msg  
                                                         delegate:self cancelButtonTitle:@"No" otherButtonTitles:@"Yes", nil];
      [alert show];
      [alert release];
  }
  
  - (void)didReceiveMemoryWarning {
      // Releases the view if it doesn't have a superview.
      [super didReceiveMemoryWarning];
  
      // Release any cached data, images, etc that aren't in use.
  }
  
  - (void)viewDidUnload {
      [super viewDidUnload];
  }
  
  
  - (void)dealloc {
      [lblMessage release];
      [managedObjectContext release];
      [super dealloc];
  }
  
  
  @end
  </code></pre>