CoreDataのデータを全て削除

(BOOL)resetDatastore
{
 [[self managedObjectContext] lock];
 [[self managedObjectContext] reset];
 NSPersistentStore *store = [[[self persistentStoreCoordinator] persistentStores] lastObject]; 
    BOOL resetOk = NO;

 if (store)
 {
        NSURL *storeUrl = store.URL;
 NSError *error;

 if ([[self persistentStoreCoordinator] removePersistentStore:store error:&error])
 {
 [[self persistentStoreCoordinator] release];
            __persistentStoreCoordinator = nil;
 [[self managedObjectContext] release];
            __managedObjectContext = nil;

 if (![[NSFileManager defaultManager] removeItemAtPath:storeUrl.path error:&error])
 {
 NSLog(@"\nresetDatastore. Error removing file of persistent store: %@",
 [error localizedDescription]);
                resetOk = NO;
 }
 else
 {
 //now recreate persistent store
 [self persistentStoreCoordinator];
 [[self managedObjectContext] unlock];
                resetOk = YES;
 }
 }
 else
 {
 NSLog(@"\nresetDatastore. Error removing persistent store: %@",
 [error localizedDescription]);
            resetOk = NO;
 }
 return resetOk;
 }
 else
 {
 NSLog(@"\nresetDatastore. Could not find the persistent store");
 return resetOk;
 }
}