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variable / @typed/fx/Fx

filterMap

Maps and filters elements of an Fx in a single operation.

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

Follow one execution

Maps and filters elements of an Fx in a single operation.

Fx timelinefilterMap omits None and emits each Some in orderfilterMap
OperatorfilterMap(toOption)
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.

This operation is stateless and acquires no resources. It preserves the source’s error and service channels and stops whenever the source or consuming fiber stops.

Source implementation · Learn the surrounding model

Compare all Fx timelines →

Import

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

Signatures

export declare const filterMap: {
    <A, B>(f: (a: A) => Option.Option<B>): <E, R>(self: Fx<A, E, R>) => Fx<B, E, R>;
    <A, E, R, B>(self: Fx<A, E, R>, f: (a: A) => Option.Option<B>): Fx<B, E, R>;
};

Why

filterMap represents a partial synchronous transformation explicitly with Option. Each input produces at most one output: Some is unwrapped and None is omitted, with source order intact.

Ownership and lifetime

This operation is stateless and acquires no resources. It preserves the source’s error and service channels and stops whenever the source or consuming fiber stops.

Examples

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

const numbers = Fx.fromIterable(["1", "x", "2"]).pipe(
  Fx.filterMap((text) => Number.isNaN(Number(text)) ? Option.none() : Option.some(Number(text))),
)

Other public imports

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

Source