The IRepository interface

Question

I am reading the source code of subsonic 3. in the file IRepository.cs I found the following:

public interface IRepository<T>
{
    IQueryable<T> GetAll();
    PagedList<T> GetPaged<TKey>(Func<T, TKey> orderBy, int pageIndex, int pageSize);
     ...many other lines
    bool Load<T>(T item, Expression<Func<T, bool>> expression) where T : class, new();
    bool Load<T>(T item, string column, object value) where T : class, new();
}

Notice the Load methods are defined as generic and their generic type names are the same as the generic type of the interface, which cause complier warnings.

My questions is: Are the Load methods really intended to be generic or it was a mistake? If the methods were intended to be generic, should we change the type name from "T" to something different like "E" in order to make the compiler happy?

Answer 1

They have constraints, unlike the class-level T, so I'd guess they're supposed to be different.

Answer 2

They're not supposed to be different - Load is supposed to work on the repos "type" so you can remove the definition there (I assume that's what you're doing)

Answer 3

Looks to me like the class and new constraints should be at the class level - not the method level.

Otherwise, yeah - you just defined 2 different T constraints which is just confusing as hell, since I could do this:

IRepository<int> intRepository = new RepositoryImpl<int>(); 

object o;
intRepository.Load<string>(o, "column", "value");

Having a IRepository<int> Load<string> seems rather odd to me.

It's possible that T must only be a class and new for the Load methods, but not the others. In that case, you may want something like:

interface IRepository<T> {
   IQueryable<T> GetAll();
   bool Load<TClass>(TClass item, string column, object value) where TClass : class, T, new();
}

which isn't exactly the same, since TClass could just inherit from T - but is the closest constraint I can think of to produce that result.

Answer 4

Well, since Rob is the author of this code. I am going to take his answer. Thanks to all you gurus for your answers.