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variable / @typed/fx

Fx.filterMapEffect

Maps and filters elements of an Fx using an effectful function.

Package version
2.0.0-beta.13
Category
Selecting values
Since
1.0.0
Member of
Fx

Follow one execution

Resolve Option results asynchronously: None drops and Some unwraps. Concurrent producers can overlap callback Effects; these rows assume serial delivery.

Fx timelinefilterMapEffect(oneTurnCallback)filterMapEffect
OperatorfilterMapEffect(oneTurnCallback)
Read this diagram

Follow each lane from left to right. Events stacked vertically share a tick; the green cursor marks the current time across every lane.

  • A value
    The text inside the pill is the emitted value.
  • Work starts
    The raised chevron starts an inner run (^ in the source).
  • The run returns
    The vertical bar ends this lane’s run.
  • A cause is delivered
    The exclamation mark belongs to this lane.
  • Work is interrupted
    The cross marks cancellation of this run.
  • Current time
    The line and diamond move together across all lanes.
  • Happening now
    A highlighted event is at the current tick.
  • Still ahead
    Muted, dashed values have not happened yet.
  • Time continues
    The lane’s arrow is not a return marker. An empty stretch can be quiet work that is still running.

Illustrated ticks start at 0. At 1×, one illustrated tick takes one second; captions specify real durations when timing matters. A cause or interruption belongs to its lane, and other work may continue. Scroll horizontally to inspect the rest of a long timeline.

Each callback Effect follows its invoking producer delivery. Its failure Cause is sent to the Sink, services remain exposed as R2, and no semaphore, queue, or resource is added.

Source implementation · Learn the surrounding model

Compare all Fx timelines →

Import

import { Fx } from "@typed/fx";

Access Fx.filterMapEffect through the imported Fx export. Its declaration below describes the member.

This public exposure is a re-export. Its import path is supported; declaration documentation is shared with the other public exposures below.

Signatures

export declare const filterMapEffect: {
    <A, B, E2, R2>(f: (a: A) => Effect.Effect<Option.Option<B>, E2, R2>): <E, R>(self: Fx<A, E | E2, R>) => Fx<B, E | E2, R | R2>;
    <A, E, R, B, E2, R2>(self: Fx<A, E | E2, R>, f: (a: A) => Effect.Effect<Option.Option<B>, E2, R2>): Fx<B, E | E2, R | R2>;
};

Why

filterMapEffect combines an Effectful decision and transformation without introducing nested streams. Some emits once and None emits nothing. Producer callbacks are not serialized, so overlapping Effects can complete and emit in a different order than their inputs.

Ownership and lifetime

Each callback Effect follows its invoking producer delivery. Its failure Cause is sent to the Sink, services remain exposed as R2, and no semaphore, queue, or resource is added.

Examples

import { Effect, Option } from "effect"
import { Fx } from "@typed/fx"

const accepted = Fx.fromIterable([1, 2]).pipe(
  Fx.filterMapEffect((n) => Effect.succeed(n > 1 ? Option.some(n * 10) : Option.none()))
)

Other public imports

These import paths expose the same declaration. Each page retains its own public name and signature.

Source