Objective-C Core Data EntityManager

If you plan to create an iPhone, iPad, or Cocoa application that requires data storage, you are going to need to use the Core Data framework. Core Data is a great framework. It saves you the pain of writing redundant data access code.. SQL, etc. Also, I really like the graphical tool used to create entity models.

However, I find the Core Data API to be overly complicated and exceedingly verbose. When compared to other modern ORM APIs, it takes a lot of work to do simple entity management tasks.

Example: Fetch a Collection of Books using Core Data

- (void) testCoreDataQuery {
 
 NSManagedObjectContext *managedObjectContext = [self managedObjectContext];
 
 
 NSFetchRequest *fetchRequest = [[[NSFetchRequest alloc] init] autorelease];
 
 fetchRequest.entity = [NSEntityDescription entityForName: @"Book" 
    inManagedObjectContext: managedObjectContext];


 NSSortDescriptor *sortDescriptor = [[[NSSortDescriptor alloc] 
           initWithKey: @"title"  ascending: YES] autorelease];
 [fetchRequest setSortDescriptors: [NSArray arrayWithObject: sortDescriptor]];

  
  
 NSFetchedResultsController *fetchResultsController = 
  [[[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest 
          managedObjectContext:managedObjectContext
         sectionNameKeyPath:nil
            cacheName:nil] autorelease];
 
 
 NSError *error = nil;
 if(![fetchResultsController performFetch:&error]) {
  NSLog(@"FETCH ERROR: %@",[error userInfo]);
 }
 
 NSArray *entities = [fetchResultsController fetchedObjects];
 
 NSLog(@"found %d books",entities.count);
 
}

That is a lot of code to write to perform what should be a really simple operation. This example doesn't even include any sort or selection criteria.

Introducing BEEntityManager

To simplify interaction with Core Data, I created a simple Entity Manager API which is inspired by the Java Persistence API. I'm guessing there are other APIs like this available, but I haven't bothered to look. Let me know if you know of any.

Example: Fetch a Collection Using BEEntityManager

- (void) testBEEntityManagerQuery {
 
 BEEntityManager *entityManager = [[[BEEntityManager alloc] init] autorelease];
 
 NSArray *books = [entityManager query: @"Book" criteria: @"author = 'F. Scott Fitzgerald'" sort: @"title" ascending: YES ];
 
 NSLog(@"found %d books",books.count);
 
 
}

This is a much easier and more maintainable way to interact with a data store. To each their own though.. it's not for everyone... some people like pain.

BEEntityManager API Features

The entity manager includes simple methods for your common data store operations.

query
get
create
createOrUpdate
save
delete

It also simplifies accessing and managing instances of NSManagedObjectContext. This is helpful in apps of any significant size.

You can download BEEntityManager from github. To see examples of how to use the API, take a look at the BEEntityManagerTest class. If you find it useful, please let me know.