passing dependencies to value resolvers

[Jon Kruger]

One thing that has made testing difficult with AutoMapper is that
value resolvers are essentially created with a service location call,
which means that if I want my value resolvers to take in constructor
dependencies, I need to have StructureMap wired up in my unit tests to
serve up the dependency to the value resolver.

What I would really like is to be able to do something like this:

public class AutoMapperConfiguration
{
public void Configure()
{
Mapper.CreateMap<Book, BookViewModel>()
.ForMember(dest => dest.Discount,
opt =>
opt.ResolveUsing<BookDiscountResolver>().FromMember(src => src.Id));
}
}

public class BookToBookViewModelMapper :
IBookToBookViewModelMapper
{
private readonly ICalculateDiscountService
_calculateDiscountService;

public BookToBookViewModelMapper(ICalculateDiscountService
calculateDiscountService)
{
_calculateDiscountService = calculateDiscountService;
}

public BookViewModel Map(Book book)
{
// *** Notice the With() call here, this is what I would
like to be able to do (or something similar) ***

Mapper.With<ICalculateDiscountService>(_calculateDiscountService).Map(book);
}
}

public class BookDiscountResolver : ValueResolver<int, decimal>
{
private readonly ICalculateDiscountService
_calculateDiscountService;

public BookDiscountResolver(ICalculateDiscountService
calculateDiscountService)
{
_calculateDiscountService = calculateDiscountService;
}

public override decimal Resolve(int id)
{
return _calculateDiscountService.CalculateDiscount(id);
}
}

I'm still on the 1.0 version of AutoMapper, so maybe this is already
possible ... thoughts?

Jon

[Jimmy Bogard]

Are you wanting the real versions of your resolvers, or stubs, or both?

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[Jon Kruger]

I want the real value resolvers, but I want to pass stubs into the resolver.

[Jimmy Bogard]

One thing you could try is go through a ServiceLocator class, instead of StructureMap, something like:

public static class ServiceLocator {

    public static Func<Type, object> LocatorFunc = t => ObjectFactory.GetInstance(t);

    public static T GetInstance<T>() {

        return (T) LocatorFunc(typeof(T));

    }

    public static object GetInstance(Type type) {

        return LocatorFunc(type);

    }

}

Then your AM config:

Mapper.Initialize(cfg => {

   cfg.ConstructServicesUsing(t => ServiceLocator.GetInstance(t));

});

And in your test, you just replace the implementation of LocatorFunc with a function that returns your stubs.  Or with an auto-mocker, I've seen that too.

HTH,

Jimmy

[Jon Kruger]

Good idea.  I think that will work.