NSFetchRequest 에 Entity 지정 방법.

NSManagedObjectContext *managedObjectContext = [self getMangedObjectContext];

// 1)방법.

NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"EntityName"];

// 2)방법.

NSEntityDescription *entityDescription = [NSEntityDescription entityForName:@"Photo" inManagedObjectContext:managedObjectContext];

NSFetchRequest *request = [[NSFetchRequest alloc] init];

[request setEntity:entityDescription];