effect-io-ai

Package: effect
Module: Layer

Layer.merge

Merges this layer with another layer concurrently, producing a new layer with combined input, error, and output types.

When to use

Use to combine an existing Layer with another Layer or an array of layers while preserving pipeline style.

Details

This is a binary version of mergeAll that merges exactly two layers or one layer with an array of layers. The layers are built concurrently and their outputs are combined.

Example (Merging two layers)

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

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

class Logger extends Context.Service<Logger, {
  readonly log: (msg: string) => Effect.Effect<void>
}>()("Logger") {}

const dbLayer = Layer.succeed(Database, {
  query: Effect.fn("Database.query")((sql: string) => Effect.succeed("result"))
})
const loggerLayer = Layer.succeed(Logger, {
  log: Effect.fn("Logger.log")((msg: string) => Effect.sync(() => console.log(msg)))
})

const mergedLayer = Layer.merge(dbLayer, loggerLayer)

See

• mergeAll for merging several layers at once

Signature

declare const merge: { <RIn, E, ROut>(that: Layer<ROut, E, RIn>): <RIn2, E2, ROut2>(self: Layer<ROut2, E2, RIn2>) => Layer<ROut | ROut2, E | E2, RIn | RIn2>; <const Layers extends [Any, ...Array<Any>]>(that: Layers): <A, E, R>(self: Layer<A, E, R>) => Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>; <RIn2, E2, ROut2, RIn, E, ROut>(self: Layer<ROut2, E2, RIn2>, that: Layer<ROut, E, RIn>): Layer<ROut | ROut2, E | E2, RIn | RIn2>; <A, E, R, const Layers extends [Any, ...Array<Any>]>(self: Layer<A, E, R>, that: Layers): Layer<A | Success<Layers[number]>, E | Error<Layers[number]>, Services<Layers[number]> | R>; }

Source

Since v2.0.0