Tutorial #4 - Printer Actor using a service Actor

In this tutorial you'll learn to start multiple Actors and how to send Events between these Actors. Unlike in the previous tutorial, however, the Printer Actor will be started as a Service.

The following new concepts are introduced:

• StartSequence::addServiceActor() method
• Service and ServiceIndex

StartSequence

The StartSequence is used to configure the initial Actors of the Engine -- right before switching to asynchronous execution.

Methods used in this tutorial are the addActor() and addServiceActor(), which are used to add Actors to the StartSequence. Actors in the StartSequence will be instantiated by the Engine in the same order as they are added.

Service and Service index

The addServiceActor method takes two template parameters: _Service and _Actor, in addition to the CPU CoreId argument.

template<class _Service, class _Actor>
void Engine::StartSequence::addServiceActor(CoreId coreId);

The _Service template corresponds to the unique tag with which the Actor will be indexed in the ServiceIndex. Any Actor can retrieve the ActorId corresponding to its _Service tag by a request to the ServiceIndex. The following code snippet shows how to query the ServiceIndex.

const ActorId printerActorId = getEngine().getServiceIndex().getServiceActorId<PrinterActor::Service>();