Dependency Injection

If your actor has a constructor that takes parameters then those need to be part of the Props as well, as described above. But there are cases when a factory method must be used, for example when the actual constructor arguments are determined by a dependency injection framework.

The basic functionality is provided by a DependencyResolver class, that can create Props using the DI container.

// Create your DI container of preference
var someContainer = ... ;

// Create the actor system
var system = ActorSystem.Create("MySystem");

// Create the dependency resolver for the actor system
IDependencyResolver resolver = new XyzDependencyResolver(someContainer, system);

When creating actorRefs straight off your ActorSystem instance, you can use the DI() Extension.

// Create the Props using the DI extension on your ActorSystem instance
var worker1Ref = system.ActorOf(system.DI().Props<TypedWorker>(), "Worker1");
var worker2Ref = system.ActorOf(system.DI().Props<TypedWorker>(), "Worker2");

Creating Child Actors using DI

When you want to create child actors from within your existing actors using Dependency Injection you can use the Actor Content extension just like in the following example.

// For example in the PreStart...
protected override void PreStart()
{
    var actorProps = Context.DI().Props<MyActor>()
        .WithRouter(/* options here */);

    var myActorRef = Context.ActorOf(actorProps, "myChildActor");
}

[!INFO] There is currently still an extension method available for the actor Context. Context.DI().ActorOf<>. However this has been officially deprecated and will be removed in future versions.

Notes

Warning

You might be tempted at times to use an IndirectActorProducer which always returns the same instance, e.g. by using a static field. This is not supported, as it goes against the meaning of an actor restart, which is described here: What Restarting Means.

When using a dependency injection framework, there are a few things you have to keep in mind.

When scoping actor type dependencies using your DI container, only TransientLifestyle or InstancePerDependency like scopes are supported. This is due to the fact that Akka explicitly manages the lifecycle of its actors. So any scope which interferes with that is not supported.

This also means that when injecting dependencies into your actor, using a Singleton or Transient scope is fine. But having that dependency scoped per httpwebrequest for example won't work.

Techniques for dependency injection and integration with dependency injection frameworks are described in more depth in the Using Akka with Dependency Injection guideline.

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Currently the following Akka.NET Dependency Injection plugins are available:

AutoFac

In order to use this plugin, install the Nuget package with Install-Package Akka.DI.AutoFac, then follow the instructions:

// Create and build your container
var builder = new Autofac.ContainerBuilder();
builder.RegisterType<WorkerService>().As<IWorkerService>();
builder.RegisterType<TypedWorker>();
var container = builder.Build();

// Create the ActorSystem and Dependency Resolver
var system = ActorSystem.Create("MySystem");
var propsResolver = new AutoFacDependencyResolver(container, system);

CastleWindsor

In order to use this plugin, install the Nuget package with Install-Package Akka.DI.CastleWindsor, then follow the instructions:

// Create and build your container
var container = new WindsorContainer();
container.Register(Component.For<IWorkerService>().ImplementedBy<WorkerService>());
container.Register(Component.For<TypedWorker>().Named("TypedWorker").LifestyleTransient());

// Create the ActorSystem and Dependency Resolver
var system = ActorSystem.Create("MySystem");
var propsResolver = new WindsorDependencyResolver(container, system);

Ninject

In order to use this plugin, install the Nuget package with Install-Package Akka.DI.Ninject, then follow the instructions:

// Create and build your container
var container = new Ninject.StandardKernel();
container.Bind<TypedWorker>().To(typeof(TypedWorker));
container.Bind<IWorkerService>().To(typeof(WorkerService));

// Create the ActorSystem and Dependency Resolver
var system = ActorSystem.Create("MySystem");
var propsResolver = new NinjectDependencyResolver(container,system);

Other frameworks

Support for additional dependency injection frameworks may be added in the future, but you can easily implement your own by implementing an Actor Producer Extension.