effect-io-ai

Package: effect
Module: Channel

Channel.mapEffect

Maps each output element with an effectful function, preserving the source channel’s done value.

When to use

Use when transforming each channel output needs an Effect, service dependency, failure channel, or configured concurrency.

Details

The mapping function receives the output element and its zero-based index. By default elements are mapped sequentially. Use options.concurrency to map multiple elements concurrently, and options.unordered to allow concurrently mapped outputs to be emitted as soon as they complete.

Example (Mapping channel output with effects)

import { Channel, Data, Effect } from "effect"

class NetworkError extends Data.TaggedError("NetworkError")<{
  readonly url: string
}> {}

// Transform values using effectful operations
const urlsChannel = Channel.fromIterable([
  "/api/users/1",
  "/api/users/2",
  "/api/users/3"
])

const fetchDataChannel = Channel.mapEffect(
  urlsChannel,
  (url) =>
    Effect.tryPromise({
      try: () => fetch(url).then((res) => res.json()),
      catch: () => new NetworkError({ url })
    })
)

// Concurrent processing with options
const numbersChannel = Channel.fromIterable([1, 2, 3, 4, 5])
const processedChannel = Channel.mapEffect(
  numbersChannel,
  (n) =>
    Effect.gen(function*() {
      yield* Effect.sleep("100 millis") // Simulate async work
      return n * n
    }),
  { concurrency: 3, unordered: true }
)

Signature

declare const mapEffect: { <OutElem, OutElem1, OutErr1, Env1>(f: (d: OutElem, i: number) => Effect.Effect<OutElem1, OutErr1, Env1>, options?: { readonly concurrency?: number | "unbounded" | undefined; readonly unordered?: boolean | undefined; }): <OutErr, OutDone, InElem, InErr, InDone, Env>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>) => Channel<OutElem1, OutErr1 | OutErr, OutDone, InElem, InErr, InDone, Env1 | Env>; <OutElem, OutErr, OutDone, InElem, InErr, InDone, Env, OutElem1, OutErr1, Env1>(self: Channel<OutElem, OutErr, OutDone, InElem, InErr, InDone, Env>, f: (d: OutElem, i: number) => Effect.Effect<OutElem1, OutErr1, Env1>, options?: { readonly concurrency?: number | "unbounded" | undefined; readonly unordered?: boolean | undefined; }): Channel<OutElem1, OutErr | OutErr1, OutDone, InElem, InErr, InDone, Env | Env1>; }

Source

Since v2.0.0