@interface CoreData ()
+ (NSURL *)coreServiceDirectory;
+ (NSManagedObjectModel *)model;
+ (NSPersistentStoreCoordinator *)coordinator;
+ (NSManagedObjectContext *)context;
+ (NSMutableSet *)coreDataErrors;

@end



@implementation CoreData
#pragma mark Initialization
static NSManagedObjectModel *s_objectModel = nil;
static NSPersistentStoreCoordinator *s_coordinator = nil;
static NSManagedObjectContext *s_context = nil;
static NSMutableSet *s_errors = nil;

+ (void)initialize {
  s_errors = [[NSMutableSet alloc] initWithCapacity:5];

  NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"my_coreDataModel" withExtension:@"momd"];
  s_objectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];

  s_coordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:s_objectModel];
  NSError *storeError = nil;
  [s_coordinator addPersistentStoreWithType:NSSQLiteStoreType
                              configuration:nil
                                        URL:[[CoreData coreServiceDirectory] URLByAppendingPathComponent:@"coredata.sqlite"]
                                    options:nil
                                      error:&storeError];
  if (storeError) {
    [s_errors addObject:storeError];
  }

  s_context = [[NSManagedObjectContext alloc] init];
  [s_context setPersistentStoreCoordinator:s_coordinator];
}

#pragma mark Class Methods
+ (NSURL *)coreServiceDirectory {
  return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}
+ (NSManagedObjectModel *)model {
  return s_objectModel;
}
+ (NSPersistentStoreCoordinator *)coordinator {
  return s_coordinator;
}
+ (NSManagedObjectContext *)context {
  return s_context;
}
+ (NSMutableSet *)coreDataErrors {
  return s_errors;
}


#pragma mark Life Cycle
- (id)init {
  if (self = [super init]) {
    self.context = [CoreData context];
    self.coordinator = [CoreData coordinator];
    self.objectModel = [CoreData model];
  }
  return self;
}

- (void)dealloc {
  self.context = nil;
  self.coordinator = nil;
  self.objectModel = nil;
  [super dealloc];
}


#pragma mark Synthesizer
@synthesize objectModel, context, coordinator;

@end