Design a common interface with Structuremap

Question

I have a common interface that takes two typical types. I want to decorate all returned versions, but since I don’t know the type when calling EnrichWith, it obviously does not compile. I tried using the EnrichWith overload, which takes place in context, thinking maybe I could capture the generic types that were passed and call Activator.CreateInstance, but the context has no useful information about this when debugging and checking.

Here is what I still have. This is my common interface:

public interface IServiceOperation<in TRequest, out TResponse> where TResponse : ServiceResult, new()
{
    TResponse PerformService(TRequest validatedRequest);
}

Here's an example implementation:

public class SignUpService : IServiceOperation<SignUpRequest, SignUpResult>
{
    private readonly IUserRepository _userRepo;

    public SignUpService(IUserRepository userRepo)
    {
        _userRepo = userRepo;
    }

    public SignUpResult PerformService(SignUpRequest validatedRequest)
    {
        var user = Mapper.Map<User>(validatedRequest);

        user.MarkAsLoggedIn();
        user.ChangePassword(validatedRequest.UnhashedPassword);

        using(var transaction = _userRepo.BeginTransaction())
        {
            _userRepo.Save(user);
            transaction.Commit();
        }

        return new SignUpResult();
    }
}

Here is my decorator who accepts another service:

public class ValidateServiceDecorator<TRequest, TResponse> : IServiceOperation<TRequest, TResponse> where TResponse : ServiceResult, new()
{
    private readonly IServiceOperation<TRequest, TResponse> _serviceOperation;
    private readonly IValidationService _validationService;

    public ValidateServiceDecorator(IServiceOperation<TRequest, TResponse> serviceOperation,
        IValidationService validationService)
    {
        _serviceOperation = serviceOperation;
        _validationService = validationService;
    }

    public TResponse PerformService(TRequest request)
    {
        var response = new TResponse();
        var validationResult = _validationService.Validate(request);

        if (!validationResult.IsValid)
        {
            response.ValidationErrors = validationResult.ValidationErrors;
            return response;
        }

        return _serviceOperation.PerformService(request);
    }

Finally, this is how far I got to the container. This does not explicitly compile, but the EnrichWith line shows what I'm trying to achieve:

public class StructureMapServiceScanner : Registry
{
    public StructureMapServiceScanner()
    {
        Scan(scanner =>
                {
                    scanner.AssemblyContainingType(typeof (IServiceOperation<,>));
                    scanner.ConnectImplementationsToTypesClosing(typeof (IServiceOperation<,>));
                });

        For(typeof (IServiceOperation<,>))
        .EnrichWith((ioc, original) => new ValidateServiceDecorator(original, ioc.GetInstance<IValidationService>()));
    }
}

, , , :

[TestClass]
public class StructureMapServiceScannerSpecs
{
    [TestMethod]
    public void Test()
    {
        ObjectFactory.Configure(cfg =>
                                    {
                                        cfg.AddRegistry<StructureMapServiceScanner>();
                                        cfg.For<IUserRepository>().Use(new Mock<IUserRepository>().Object);
                                        cfg.For<IValidationService>().Use(new Mock<IValidationService>().Object);
                                    });

        var service = ObjectFactory.GetInstance<IServiceOperation<SignUpRequest, SignUpResult>>();

        service.ShouldNotBeNull();
        service.ShouldBeType<ValidateServiceDecorator<SignUpRequest, SignUpResult>>();
    }
}

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Answer 1

, . :

public class ServiceRegistrationConvention : IRegistrationConvention
{
    public void Process(Type type, Registry registry)
    {
        var interfacesImplemented = type.GetInterfaces();

        foreach (var interfaceImplemented in interfacesImplemented)
        {
            if (interfaceImplemented.IsGenericType && interfaceImplemented.GetGenericTypeDefinition() == typeof(IServiceOperation<,>))
            {
                var genericParameters = interfaceImplemented.GetGenericArguments();
                var closedValidatorType = typeof(ValidateServiceDecorator<,>).MakeGenericType(genericParameters);

                registry.For(interfaceImplemented)
                    .EnrichWith((context, original) => Activator.CreateInstance(closedValidatorType, original,
                                                                                context.GetInstance<IValidationService>()));
            }
        }
    }
}

Answer 2

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public class ServiceRegistrationConvention : IRegistrationConvention
{
    public void Process(Type type, Registry registry)
    {
        var handlerInterfaces = (from t in type.GetInterfaces()
                                 where t.IsGenericType &&
                                       t.GetGenericTypeDefinition() == typeof (IHandle<,>)
                                 select t);

        foreach (var handler in handlerInterfaces)
        {
            var decoratorType = typeof (ValidationDecorator<,>).MakeGenericType(handler.GetGenericArguments());

            registry.For(handler)
                .EnrichWith((ctx, orig) => ObjectFactory.With(handler, orig).GetInstance(decoratorType));
        }
    }
}

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