inversion of control - Does Castle-Windsor support ForwardedTypes via XML configuration

Question

I have a class that implements multiple interfaces. I would like to register these interfaces via XML. All I've found is documentation for the new Fluent Interface. Is this option supported via XML? What would be involved in adding this feature?

Answer 1

[Update] This is now possible in Windsor 2.1 or newer. See the documentation for syntax here.

---

This feature has not been implemented in the XML interpreter as of yet.. however it is not difficult to add support for it via a facility (obviously this technique is also useful when wanting to add other features absent from the existing configuration parser).

So first off we add a facility which will detect when a handler is created for a type, and at the same time will register any of the forwarded services so they point to the existing handler:

public class HandlerForwardingFacility : AbstractFacility
{
  IConversionManager conversionManager;

  protected override void Init()
  {
    conversionManager = (IConversionManager)Kernel.GetSubSystem(SubSystemConstants.ConversionManagerKey);
    Kernel.HandlerRegistered += new HandlerDelegate(Kernel_HandlerRegistered);      
  }

  void Kernel_HandlerRegistered(IHandler handler, ref bool stateChanged)
  {
    if (handler is ForwardingHandler) return;

    var model = handler.ComponentModel;

    if (model.Configuration == null) return;

    var forward = model.Configuration.Children["forward"];
    if (forward == null) return;

    foreach (var service in forward.Children)
    {
      Type forwardedType = (Type)conversionManager.PerformConversion(service, typeof (Type));
      Kernel.RegisterHandlerForwarding(forwardedType, model.Name);
    }
  }
}

And then of course we need to make use of this in code, for this example I'm going to have a mutant duck/dog component that supports two separate services - IDuck and IDog:

public interface IDog
{
  void Bark();
}

public interface IDuck
{
  void Quack();
}

public class Mutant : IDog, IDuck
{
  public void Bark()
  {
    Console.WriteLine("Bark");
  }

  public void Quack()
  {
    Console.WriteLine("Quack");
  }
}

Now to actually configure the container:

 <castle>
  <facilities>
    <facility id="facility.handlerForwarding" type="Example.Facilities.HandlerForwardingFacility, Example" />
  </facilities>
  <components>
    <component id="mutant" service="Example.IDog, Example" type="Example.Mutant, Example">
      <forward>
        <service>Example.IDuck, Example</service>
      </forward>
    </component>
  </components>
</castle>

And now we can happily execute a test like this:

  WindsorContainer container = new WindsorContainer(new XmlInterpreter());

  var dog = container.Resolve<IDog>();
  var duck = container.Resolve<IDuck>();

  Assert.AreSame(dog, duck);

Hope this helps.