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Fx.exhaustLatestMapEffect

Maps each element to an Effect, running one now and retaining only the latest waiting value.

Package version
2.0.0-beta.13
Category
Concurrent work
Since
1.0.0
Member of
Fx

Follow one execution

b is replaced by c in the single pending slot. Active a is allowed to finish.

Fx timelineexhaustLatestMapEffect(index)exhaustLatestMapEffect
OperatorexhaustLatestMapEffect(index)
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.

Source and admitted Effect failures remain typed, as do callback service requirements. The required Scope owns the active Effect; source completion drains the final pending value, while interruption discards pending work and runs active finalizers.

Source implementation · Learn the surrounding model

Compare all Fx timelines →

Import

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

Access Fx.exhaustLatestMapEffect 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 exhaustLatestMapEffect: FlatMapEffectLike;

Why

This is the Effect-producing form of {@link exhaustLatestMap }: it serializes Effects while bounding pending work to one replaceable latest request.

Admission, buffering, and cardinality

The first value while idle starts one Effect. While it runs, each callback is evaluated and the constructed Effect replaces the single pending Effect. Each admitted Effect emits exactly one successful result; superseded pending Effects never run and emit nothing.

Ownership and lifetime

Source and admitted Effect failures remain typed, as do callback service requirements. The required Scope owns the active Effect; source completion drains the final pending value, while interruption discards pending work and runs active finalizers.

Examples

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

const refreshes = Fx.mergeAll(
  Fx.at("v1", "0 millis"),
  Fx.at("v2", "5 millis"),
  Fx.at("v3", "10 millis")
)
const indexed = Fx.exhaustLatestMapEffect(refreshes, (version) =>
  Effect.as(Effect.sleep("20 millis"), `indexed:${version}`)
)

Effect.runPromise(Effect.scoped(Fx.collectAll(indexed))).then(console.log)
// ["indexed:v1", "indexed:v3"]

Other public imports

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

Source