event

Part of the host contract in host.wit. This interface answers questions about the event a hook is handling, past the three facts the context record already carries. Each function takes the event id and answers about that event alone; an id that is not the one in flight is refused, never answered for the current one — which is what keeps these reads from becoming an ambient read of whatever ran last.

Imported by both worlds: server-mod and client-mod.

Both functions are synchronous in spirit, like resolve: they read state the store already holds. A refusal is the error record.

cause-of

cause-of: func(event: event-id) -> result<option<cause>, error>;

Who caused this event, as a cause. The answer is absent where the realm cannot name one: a client half does not know the participant at its own machine. Refuses when event is not the event this hook is handling.

instance-of

instance-of: func(event: event-id) -> result<instance-token, error>;

The subject instance’s generational token, for a handler that holds a handle across events. Entity ids are reused, the token is not, so a stale holder can never address this tick’s stranger. Refuses when event is not the event this hook is handling, and when the event has no subject.

Related

• types — context, cause, instance-token
• server-api and client-api — the hooks that receive a context
• Mod lifecycle — when hooks run