Unity IoC Newbie - Constructor Injection fail!

Question

Hi

I'm just starting trying to work with the Unity IoC framework, but I'm struggling to get the container resolving properly when it has a parameter in the constructor.

I was watching Dave Hayden's webcast and it seems that I don't need to register the class I want to construct.

So I have a class which wraps unity

    public class UnityContainer : IContainer

    {

        private Microsoft.Practices.Unity.IUnityContainer _container;

        public UnityContainer()

        {

            _container = new Microsoft.Practices.Unity.UnityContainer()

                .RegisterType<IChannel, SimpleEvent>()

                .RegisterType<IChannelID, ChannelID>();

            //_container.Configure<InjectedMembers>().ConfigureInjectionFor<Broker>(new InjectionConstructor(new ChannelFactory));

        }

        public T Resolve<T>()

        {

            return (T) _container.Resolve<T>();

        }

    }

I also have another class which I want to construct with unity

   public class Broker : IBroker

    {

        ChannelFactory _factory;

        

        public Broker(ChannelFactory factory)

        {

            _factory = factory;

        }

 ...

    public class ChannelFactory

    {

        private readonly IContainer _container;

        public ChannelFactory(IContainer container)

        { 

            _container = container;

        }

...

In my test I have

        [TestMethod]

        public void T5_Create_Broker_With_Unity()

        { 

            IContainer container = new UnityContainer();

            IBroker broker = container.Resolve<Broker>();

        }

When I run the test code it fails ... telling me "The parameter factory could not be resolved when attempting to call constructor ... Are you missing a type mapping?" I did try and register the type, but it didn't make any difference. (Full error below)

I must be doing something pretty elementary wrong! I'd be grateful if someone could point out what I am missing. 

Many Thx

Simon

Error text

Test method Test_CommunicationsBroker.BrokerTests.T5_Create_Broker_With_Unity threw exception:  Microsoft.Practices.Unity.ResolutionFailedException: Resolution of the dependency failed, type = "MessageRouter.Broker", name = "". Exception message is: The current build operation (build key Build Key[MessageRouter.Broker, null]) failed: The parameter factory could not be resolved when attempting to call constructor MessageRouter.Broker(MessageRouter.ChannelFactory factory). (Strategy type BuildPlanStrategy, index 3) --->  Microsoft.Practices.ObjectBuilder2.BuildFailedException: The current build operation (build key Build Key[MessageRouter.Broker, null]) failed: The parameter factory could not be resolved when attempting to call constructor MessageRouter.Broker(MessageRouter.ChannelFactory factory). (Strategy type BuildPlanStrategy, index 3) --->  System.InvalidOperationException: The parameter factory could not be resolved when attempting to call constructor MessageRouter.Broker(MessageRouter.ChannelFactory factory). --->  Microsoft.Practices.ObjectBuilder2.BuildFailedException: The current build operation (build key Build Key[MessageRouter.ChannelFactory, null]) failed: The parameter container could not be resolved when attempting to call constructor MessageRouter.ChannelFactory(MessageRouter.IContainer container). (Strategy type BuildPlanStrategy, index 3) --->  System.InvalidOperationException: The parameter container could not be resolved when attempting to call constructor MessageRouter.ChannelFactory(MessageRouter.IContainer container). --->  Microsoft.Practices.ObjectBuilder2.BuildFailedException: The current build operation (build key Build Key[MessageRouter.IContainer, null]) failed: The current type, MessageRouter.IContainer, is an interface and cannot be constructed. Are you missing a type mapping? (Strategy type BuildPlanStrategy, index 3) --->  System.InvalidOperationException: The current type, MessageRouter.IContainer, is an interface and cannot be constructed. Are you missing a type mapping?.

Answer 1

OK so I've sort of sorted it.

Trying to get unity to construct this

 public class ChannelFactory

    {

        private readonly IContainer _container;

        public ChannelFactory(IContainer container)

        { 

            _container = container;

        }

...

was the problem. It wasn't able to resolve the IContainer for some reason (lack of understanding on my part rather than a failure of unity, btw).

Is it good practice or perhaps even necessary for the  container to be in a static class?

Thx

S