Resolving named dependencies with Unity

Question

I have a service with 2 dependencies: a Repository and a Gateway (sms).

I need to resolve 2 different versions of the service that only differ on one of the parameters passed to the gateway.

The code is simplified to as follows

public interface IService
{
    string DoSomething();
}

public interface IServiceFoo
{
    string DoSomething();
}

public interface IServiceBar
{
    string DoSomething();
}

public interface IRepository { }
public class Repository : IRepository { }

public interface IGateway
{
    string Name { get; set; }
}

public class Gateway : IGateway
{
    public string Name { get; set; }
    public Gateway(string name)
    {
        this.Name = name;
    }
}

public class Service : IService, IServiceFoo, IServiceBar
{
    private readonly IGateway _gateway;
    private readonly IRepository _repo;
    public Service(IRepository repo, IGateway gateway)
    {
        _gateway = gateway;
        _repo = repo;
    }

    public string DoSomething()
    {
        return _gateway.Name;
    }
}

Failing test

[TestClass]
public class UnityTest
{
    [TestMethod]
    public void TestMethod1()
    {
        var container = new UnityContainer();
        container
            .RegisterType<IRepository, Repository>()
            .RegisterType<IGateway, Gateway>("FooGateway", new InjectionConstructor("I am foo"))
            .RegisterType<IGateway, Gateway>("BarGateway", new InjectionConstructor("I am bar"))
            .RegisterType<IServiceFoo, Service>(new InjectionConstructor(new ResolvedParameter<IRepository>(), new ResolvedParameter<IGateway>("FooGateway")))
            .RegisterType<IServiceBar, Service>(new InjectionConstructor(new ResolvedParameter<IRepository>(), new ResolvedParameter<IGateway>("BarGateway")));

        var barGateway = container.Resolve<IGateway>("BarGateway");
        var fooGateway = container.Resolve<IGateway>("FooGateway");

        var serviceBar = container.Resolve<IServiceBar>();
        var serviceBarGatewayName = serviceBar.DoSomething();

        var serviceFoo = container.Resolve<IServiceFoo>();
        var serviceFooGatewayName = serviceFoo.DoSomething();

        Assert.AreEqual("I am bar", barGateway.Name); // pass
        Assert.AreEqual("I am foo", fooGateway.Name); // pass


        Assert.AreEqual("I am bar", serviceBarGatewayName); // pass
        Assert.AreEqual("I am foo", serviceFooGatewayName); // FAIL

The wrong gateway is being passed in when the service is resolved, however if I resolve the gateway explicitly by name, it comes out correct. I think I'm missing something fundamental in how ResolvedParameter(string name) is working but I assumed that it looks for a type in the container with that name.

Answer 1

Still have no idea why your version doesn't work but this DOES work (as I've expected):

        var container = new UnityContainer();
        container
            .RegisterType<IRepository, Repository>()
            .RegisterType<IGateway, Gateway>( "FooGateway", new InjectionConstructor( "I am foo" ) )
            .RegisterType<IGateway, Gateway>( "BarGateway", new InjectionConstructor( "I am bar" ) )
            //.RegisterType<IServiceFoo, Service>( new InjectionConstructor( new ResolvedParameter<IRepository>(), new ResolvedParameter<IGateway>( "FooGateway" ) ) )
            //.RegisterType<IServiceBar, Service>( new InjectionConstructor( new ResolvedParameter<IRepository>(), new ResolvedParameter<IGateway>( "BarGateway" ) ) );
            .RegisterType<IServiceFoo>( new InjectionFactory( c => new Service( c.Resolve<IRepository>(), c.Resolve<IGateway>( "FooGateway" ) ) ) )
            .RegisterType<IServiceBar>( new InjectionFactory( c => new Service( c.Resolve<IRepository>(), c.Resolve<IGateway>( "BarGateway" ) ) ) );

Note that I am using InjectionFactory instead of InjectionConstructor.

Yet another version that works. This time I keep your way of registering services but I make them named and resolve by name:

        var container = new UnityContainer();
        container
            .RegisterType<IRepository, Repository>()
            .RegisterType<IGateway, Gateway>( "FooGateway", new InjectionConstructor( "I am foo" ) )
            .RegisterType<IGateway, Gateway>( "BarGateway", new InjectionConstructor( "I am bar" ) )
            .RegisterType<IServiceFoo, Service>( "sf", new InjectionConstructor( new ResolvedParameter<IRepository>(), new ResolvedParameter<IGateway>( "FooGateway" ) ) )
            .RegisterType<IServiceBar, Service>( "sb", new InjectionConstructor( new ResolvedParameter<IRepository>(), new ResolvedParameter<IGateway>( "BarGateway" ) ) );
            //.RegisterType<IServiceFoo>( new InjectionFactory( c => new Service( c.Resolve<IRepository>(), c.Resolve<IGateway>( "FooGateway" ) ) ) )
            //.RegisterType<IServiceBar>( new InjectionFactory( c => new Service( c.Resolve<IRepository>(), c.Resolve<IGateway>( "BarGateway" ) ) ) );


        var barGateway = container.Resolve<IGateway>( "BarGateway" );
        var fooGateway = container.Resolve<IGateway>( "FooGateway" );

        var serviceBar = container.Resolve<IServiceBar>( "sb" );
        var serviceBarGatewayName = serviceBar.DoSomething();

        var serviceFoo = container.Resolve<IServiceFoo>( "sf" );
        var serviceFooGatewayName = serviceFoo.DoSomething();

Answer 2

it can also be done using ParameterOverride as below

        container
            .RegisterType<IRepository, Repository>()
            .RegisterType<IGateway, Gateway>("FooGateway", new InjectionConstructor("I am foo"))
            .RegisterType<IGateway, Gateway>("BarGateway", new InjectionConstructor("I am bar"))
            .RegisterType<IServiceFoo, Service>(new InjectionConstructor(new ResolvedParameter<IRepository>(), typeof(IGateway)))
            .RegisterType<IServiceBar, Service>(new InjectionConstructor(new ResolvedParameter<IRepository>(), typeof(IGateway)));

        var barGateway = container.Resolve<IGateway>("BarGateway");
        var fooGateway = container.Resolve<IGateway>("FooGateway");

        var serviceBar = container.Resolve<IServiceBar>(new ParameterOverride("gateway", barGateway));
        var serviceBarGatewayName = serviceBar.DoSomething();

        var serviceFoo = container.Resolve<IServiceBar>(new ParameterOverride("gateway", fooGateway));
        var serviceFooGatewayName = serviceFoo.DoSomething();

        Assert.AreEqual("I am bar", barGateway.Name); // pass
        Assert.AreEqual("I am foo", fooGateway.Name); // pass


        Assert.AreEqual("I am bar", serviceBarGatewayName); // pass
        Assert.AreEqual("I am foo", serviceFooGatewayName); // pass