Castle Windsor：开放泛型类型的条件注册

Question

I have the following:

class Repository<T> : IRepository<T>
interface ISuperRepository<T> : IRepository<T>
class SuperRepository<T> : ISuperRepository<T>
interface ISuperType

I want conditional registration in Castle Windsor DI for IRepository<T> , if T is ISuperType , then provide ISuperRepository<T> . Else, provide IRepository<T>.

So for example, if A : ISuperType , then I want Resolve<IRepository<A>> to provide SuperRepository<A> , and Resolve<IRepository<B>> to provide Repository<B> .

How can I achive that?

Answer 1

Castle Windsor doesn't support such a thing, however you can achieve it with a simple helper method:

public static void RegisterAccordingToISuperType<T>(this IWindsorContainer container)
{
    if (typeof (T).GetInterfaces().Contains(typeof (ISuperType)))
        container.Register(Component.For<IRepository<T>>()
                                    .ImplementedBy<SuperRepository<T>>());
    else
        container.Register(Component.For<IRepository<T>>()
                                    .ImplementedBy<Repository<T>>());
}

Then the registration:

container.RegisterAccordingToISuperType<SuperType>();
container.RegisterAccordingToISuperType<int>();

And the resolve will:

var super = container.Resolve<IRepository<SuperType>>();
var intRepo = container.Resolve<IRepository<int>>();

Another option is to the extra parameter in Component.For . Then gets all type which inherite form the Type( For example ) and register them.

private static void Register(...)
{
    foreach (var type in GetInheriteTypes())
    {          
        container.Register(Component.For(typeof(IRepository<>),type)
                                    .ImplementedBy(typeof(SuperRepository<>)));
    }
    container.Register(Component.For(typeof(IRepository<>))
                                .ImplementedBy(typeof(Repository<>)));
}

private static IEnumerable<Type> GetInheriteTypes()
{
    var listOfBs = (from domainAssembly in AppDomain.CurrentDomain.GetAssemblies()
                    from assemblyType in domainAssembly.GetTypes()
                    where assemblyType.GetInterfaces().Contains(typeof(ISuperType))
                    select assemblyType).ToArray();
    return listOfBs;
}

Answer 2

You can restrict what types a generic is used for with the "where T: typename" syntax, where "typename" refers to a type the specified type 'T' must inherit (or implement). In your case "where T: ISuperType" would match the specific types, and a version without the restriction should match all the rest.

ref. https://msdn.microsoft.com/en-us/library/bb384067.aspx

If it can't be done at compile-time, it can always be done at runtime (with f.ex. 'is').