Question

Trying to avoid the SomethingManager trap here…

Let’s say I’m going to write a User editor which will allow administrators to create users in the system. Pretty basic functionality – view a list of existing users, create a new user, update an existing user, delete a user.

Let us also say that I decide to write a “business” class to handle these basic CRUD operations. This is probably what the interface would look like:

public interface ISomeUsefulName
{
    IList<User> FetchUsers();
    User FetchUser(int userId);
    bool SaveUser(User user);
    bool DeleteUser(int userId);
}

Inside the SaveUser() method, for example, I would validate the data (using a different class) and then actually save the data to the database (again using another class).

My question is, what should I name this class? Is this class doing too much and therefore I should split it into multiple classes?

Answer 1

Naming is difficult if is not respected SRP 🙂
But members naming is often misused.

In your case I’ll do something like this:

• the responsibility of implementation is to cover specified contract of persistence
• “who” is under fire

Thinks without voice
– persistence is done for user and a relevant name can be IUserRepository
– methods are not more than for CRUD
– because of the fact that the IUserRepository is for user, is not necessary to have UserSave, UserUpdate because it brakes the generic usage manner

The Magic Is Here … just do this:

public interface IRepository<TYPE, KEY>{
  IList<TYPE> GetAll(KEY key);
  TYPE GetById(KEY key);
  void Save(TYPE obj);
  void Update(TYPE obj);
  void Delete(Key key);
}

Is it difficult ?
What to do with a custom one?

public interface IUserRepository : IRepository<User, int>
{
   IList<User> GetAllMyFavorites(ICriteria crit);
   IList<Events> GetHistoryByUser(User user);   
}

In the code using an IoC container you can do easily

public UserController {
  private _userRepository = null;
  private _eventsRepository = null;

  public UserController(IUserRepository userRepository, 
  IRepository<Events,int> eventsRepository) 
  // if you are doing here just CRUD use the generic signature
  {
    _userRepository = userRepository;
    _eventsRepository = eventsRepository;
  }

  public MarkItAsGoldPartener(int userId){
     var user = userRepository.GetById(userId);
     user.PartnerType = PartnerTypes.Gold;
     userRepository.Save(user); // the user in member name is useless
     eventsRepository.Save(new Event(){Message = "The user" + UserId + "is golden" });
  }
} 

good luck 🙂