# subscribe(to:on:componentType:_:) Subscribes to an event type, optionally limited to events affecting a source entity or scene, or a specific component type for component events. ``` func subscribe(to event: E.Type, on sourceObject: (any EventSource)?, componentType: (any Component.Type)?, _ handler: @escaping (E) -> Void) -> EventSubscription where E : Event ``` ## Parameters `event` The event type to subscribe to. For example, [`SceneEvents.Update`](/documentation/RealityKit/SceneEvents/Update) or [`ComponentEvents.DidActivate`](/documentation/RealityKit/ComponentEvents/DidActivate). `sourceObject` An optional source for the event, such as an entity or a scene. Set to `nil` to listen for all events of the event type within the [`RealityViewContent`](/documentation/RealityKit/RealityViewContent). `componentType` An optional component type to filter events to if the event is of the type [`ComponentEvents`](/documentation/RealityKit/ComponentEvents). Set to `nil` to listen for all events of the event type within the [`RealityViewContent`](/documentation/RealityKit/RealityViewContent). `handler` A closure that runs when the `event` occurs. ## Return Value An object that represents the subscription to this event stream. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)