Method next

packages/core/src/StateNode.ts:366–429

@internal

(
    snapshot: MachineSnapshot<
      TContext,
      TEvent,
      any,
      any,
      any,
      any,
      any, // TMeta
      any // TStateSchema
    >,
    event: TEvent
  )

  /** @internal */
  public next(
    snapshot: MachineSnapshot<
      TContext,
      TEvent,
      any,
      any,
      any,
      any,
      any, // TMeta
      any // TStateSchema
    >,
    event: TEvent
  ): TransitionDefinition<TContext, TEvent>[] | undefined {
    const eventType = event.type;
    const actions: UnknownAction[] = [];

    let selectedTransition: TransitionDefinition<TContext, TEvent> | undefined;

    const candidates: Array<TransitionDefinition<TContext, TEvent>> = memo(
      this,
      `candidates-${eventType}`,
      () => getCandidates(this, eventType)
    );

    for (const candidate of candidates) {
      const { guard } = candidate;
      const resolvedContext = snapshot.context;

      let guardPassed = false;

      try {
        guardPassed =
          !guard ||
          evaluateGuard<TContext, TEvent>(
            guard,
            resolvedContext,
            event,
            snapshot
          );
      } catch (err: any) {
        const guardType =
          typeof guard === 'string'
            ? guard
            : typeof guard === 'object'
              ? guard.type
              : undefined;
        throw new Error(
          `Unable to evaluate guard ${
            guardType ? `'${guardType}' ` : ''
          }in transition for event '${eventType}' in state node '${
            this.id
          }':\n${err.message}`
        );
      }

      if (guardPassed) {
        actions.push(...candidate.actions);
        selectedTransition = candidate;