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ReactionResolver

@rotorsoft/act-root

@rotorsoft/act-root / act/src / ReactionResolver

Type Alias: ReactionResolver<TEvents, TKey>

ReactionResolver<TEvents, TKey> = { source?: string; target: string; } | (event) => { source?: string; target: string; } | undefined

Defined in: libs/act/src/types/reaction.ts:106

Resolver for determining which stream a reaction should target.

Resolvers enable dynamic reaction routing based on event content. They can be:

  • Static: Always route to the same target stream
  • Dynamic: Determine target based on event data at runtime

Resolvers can also specify source streams for optimization, allowing the drain process to efficiently fetch only relevant events.

Type Parameters​

TEvents​

TEvents extends Schemas

Event schemas

TKey​

TKey extends keyof TEvents

Event name

Param​

The committed event (for dynamic resolvers)

Returns​

Target stream configuration or undefined to skip

Examples​

.on("UserCreated")
  .do(sendWelcomeEmail)
  .to("email-queue") // Static target
.on("UserLoggedIn")
  .do(incrementLoginCount)
  .to((event) => ({
    target: `stats-${event.stream}` // Dynamic per user
  }))
.on("UserUpdated")
  .do(updateReadModel)
  .to(({ stream }) => ({
    source: stream,           // Only fetch from this user's stream
    target: `cache-${stream}` // Update corresponding cache
  }))

See​

Reaction for complete reaction configuration