@ue-too/being / index / EventPreconditions

型エイリアス: EventPreconditions<EventPayloadMapping, Context, T>

EventPreconditions<EventPayloadMapping, Context, T> = { [K in keyof EventPayloadMapping]: (T extends Guard<Context, infer G> ? G : never)[] }

定義: interface.ts:585

型パラメーター

EventPayloadMapping

EventPayloadMapping

Context

Context extends BaseContext

T

T extends Guard<Context>

Description

Per-event preconditions: named guards that must ALL pass before a state handles an event.

Remarks

Preconditions are evaluated at the very start of TemplateState.handles, before the defer hook and before the event's reaction runs. If any listed guard evaluates to false — or names a guard missing from the state's State.guards registry (fail closed) — the event is vetoed: the state returns { handled: false }, no action runs, and no transition occurs. An unhandled result lets hierarchical machines bubble the event to a parent.

This differs from EventGuards, which run AFTER the action to pick a target state. The same named guards from the state's guard registry can be referenced by both.

Generic parameters:

• EventPayloadMapping: A mapping of events to their payloads.
• Context: The context of the state machine.
• T: The guard type (its keys become the valid precondition names).