I want to register a generic delegate that resolves itself at runtime, but I cannot find a way to do this on generics.
Given a delegate that looks like this:
public delegate TOutput Pipe<in TInput, out TOutput>(TInput input);
And given a discretely registered delegate that look like this:
public class AnonymousPipe<TInput, TOutput>
{
public Pipe<TInput, TOutput> GetPipe(IContext context)
{...}
I want to register a function along the lines of this:
builder.RegisterGeneric(typeof(Pipe<,>)).As(ctx =>
{
var typeArray = ctx.RequestedType.GetGenericArguments();
// this can be memoized
var pipeDefinition = ctx.Resolve(typeof(AnonymousPipe<,>).MakeGenericType(typeArray));
return pipeDefinition.GetPipe(ctx);
I cannot find a way to provide an implementation of the generic as a parameter in Autofac - I may just be missing something. I know I can do this through a generic object or interface, but I want to stick with the lightness of a delegate. It makes unit testing super simple on the injection of these.
Any thoughts? I am having to do discrete registrations at the moment(one per type combination and no generics).
I can only come up with the registration source solution (the universal hammer in Autofac.)
class PipeSource : IRegistrationSource
{
public bool IsAdapterForIndividualComponents { get { return true; } }
public IEnumerable<IComponentRegistration> RegistrationsFor(
Service service,
Func<Service, IEnumerable<IComponentRegistration>> registrationAccessor)
{
var swt = service as IServiceWithType;
if (swt == null || !swt.ServiceType.IsGenericType)
yield break;
var def = swt.ServiceType.GetGenericTypeDefinition();
if (def != typeof(Pipe<,>))
yield break;
var anonPipeService = swt.ChangeType(
typeof(AnonymousPipe<,>).MakeGenericType(
swt.ServiceType.GetGenericArguments()));
var getPipeMethod = anonPipeService.ServiceType.GetMethod("GetPipe");
foreach (var anonPipeReg in registrationAccessor(anonPipeService))
{
yield return RegistrationBuilder.ForDelegate((c, p) => {
var anon = c.ResolveComponent(anonPipeReg, p);
return getPipeMethod.Invoke(anon, null); })
.As(service)
.Targeting(anonPipeReg)
.CreateRegistration();
}
}
}
Then:
builder.RegisterSource(new PipeSource());
Now, I'm certain that I can't type that code into a web page and have it actually compile and run, but it might come close :)
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