What are the MixedRealityServiceRegistry and IMixedRealityServiceRegistrar?

The Mixed Reality Toolkit has two very similarly named components that perform related tasks: MixedRealityServiceRegistry and IMixedRealityServiceRegistrar.

MixedRealityServiceRegistry

The MixedRealityServiceRegistry is the component that contains instances of each registered service (core systems and extension services).

Note

The MixedRealityServiceRegistry contains instances of objects that implement IMixedRealityService interface, including IMixedRealityExtensionService.

Objects implementing the IMixedRealityDataProvider (a subclass of IMixedRealityService) are explicitly not registered in the MixedRealityServiceRegistry. These objects are managed by the individual services (ex: Spatial Awareness).

The MixedRealityServiceRegistry is implemented as a static C# class and is the recommended pattern to use to acquire service instances in application code.

The following snippet demonstrates acquiring an IMixedRealityInputSystem instance.

IMixedRealityInputSystem inputSystem = null;

if (!MixedRealityServiceRegistry.TryGetService<IMixedRealityInputSystem>(out inputSystem))
{
    // Failed to acquire the input system. It may not have been registered
}

IMixedRealityServiceRegistrar

The IMixedRealityServiceRegistrar is the interface that defines the functionality implemented by components that manage the registration of one or more services. Components that implement IMixedRealityServiceRegistrar are responsible for adding and removing the data within the MixedRealityServiceRegistry. The MixedRealityToolkit object is one such component.

Other registrars can be found in the MRTK/SDK/Experimental/Features folder. These components can be used to add single service (ex: Spatial Awareness) support to an application. These single service managers are listed below.

Each of the above components, with the exception of the InputSystemManager, are responsible for managing the registration and status of a single service type. The InputSystem requires some additional support services (ex: FocusProvider) that are also managed by the InputSystemManager.

In general, the methods defined by IMixedRealityServiceRegistrar are called internally by service management components or called by services that require additional service components to function correctly. Application code should, generally, not call these methods as doing so may cause the application to behave unpredictably (ex: a cached service instance may become invalid).

See also