Proper Repository Design, Attaching one Object to Another

Question

In my attempt to keep with a good Repository/IoC Design, I am trying to figure out the best approach the current problem.

There are two objects, Member , and Character .

Basically, one Member can have many characters. Simple enough.

Member
{
 IList<Character> Characters { get; set; }
}

There is an IMemberRepository ...

interface IMemberRepository
{
 MemberCreateStatus CreateMember(string email, string password);
 bool ValidateMember(string email, string password);
 bool ChangePassword(string email, string password, string newPassword);
 void RecoverPassword(string email);
}

And there is an ICharacterRepository

interface ICharacterRepository
{
 Character CreateCharacter(string name);
}

So then, my question is quite simple. Where do I want to add the logic to add a Character to a Member ? Do I do this in IMemberRepository ? That seems cumbersome to me. It seems beyond the scope of the IMemberRepository 's tasks. Do I add it to the ICharacterRepository ? That too seems a bit strange to me, because giving that knowledge of the Membership seems to be in violation of keeping them separated. What's the best approach to take, here?

If it were just this one method, it wouldn't be too big a deal - but there will be a lot of other things that have to occur between the two classes. What's the 'standards' way to approach this situation of two objects relating to one another? I am coding this in ASP.NET MVC .

Answer 1

I think you are maybe approaching Repositories a little differently than intended, and that may be the cause of some of your confusion.

Repositories are to provide collection semantics to a set of data. That means Repositories Get, Add, and Remove stuff. They don't validate. They don't change things about individual items. They are not a Data Access Object (DAO), though it seems many people lately name a thing Repository and then make it look like a DAO.

Your Member contains a list of Characters. Great! Want to add a Character to a Member? Do exactly that. Member.AddCharacter(...) or Member.Characters.Add(...) . I usually use the former, but the latter can work as well (but requires custom collection implementations).

Answer 2

I feel it is responsibility of IMemberRepository to populate Characters of a Member . There are a few reasons:

• Since IMemberRepository is Member type's Repository , it knows what Member is composed of. And that is why it knows about Character type.
• It is certainly not ICharacterRepository 's responsibility. Character type can be used to compose other types in future. That will affect Character 's Repository whenever you add new type.
• IMemberRepository will be using ICharacterRepository to populate Character objects in Member .

Answer 3

The most natural approach for me is to put that logic inside the Member class as the Member object is responsible of tracking its own Characters.

What do you think about that?