effect-io-ai

Package: effect
Module: LayerRef

LayerRef.make

Creates a LayerRef from a Layer.

When to use

Use when you have one layer-built resource that should be shared, optionally kept alive while idle, and refreshed on demand.

Details

The layer is built lazily on first use unless preload is true. idleTimeToLive keeps the context cached after it stops being used, and invalidationSchedule can periodically invalidate it. When preload is true, scheduled invalidation also reacquires the context.

Gotchas

Invalidation does not revoke contexts already borrowed by active scopes; those contexts remain usable until their scopes close.

Example (Sharing one layer-built service)

import { Context, Effect, Layer, LayerRef } from "effect"

class Database extends Context.Service<Database, {
  readonly query: Effect.Effect<string>
}>()("Database") {}

const databaseLayer = Layer.succeed(Database, {
  query: Effect.succeed("result")
})

const query = Effect.gen(function*() {
  const database = yield* Database
  return yield* database.query
})

const program = Effect.scoped(
  Effect.gen(function*() {
    const ref = yield* LayerRef.make(databaseLayer, {
      idleTimeToLive: "5 seconds"
    })

    const result = yield* Effect.provide(query, ref.get)

    yield* ref.invalidate

    return result
  })
)

See

• Service for defining a reusable service class around a LayerRef

Signature

declare const make: <I, E, R, X, const Preload extends boolean = never, SE = never, SR = never>(layer: Layer.Layer<I, E, R>, options?: { readonly idleTimeToLive?: Duration.Input | undefined; readonly preload?: Preload | undefined; readonly invalidationSchedule?: Schedule.Schedule<X, unknown, SE, SR> | undefined; } | undefined) => Effect.Effect<LayerRef<I, E>, [Preload] extends [true] ? E : never, Scope.Scope | R | SR>

Source

Since v4.0.0