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variable / @typed/fx

Fx.suspend

Defers creation of an Fx until each run begins.

Package version
2.0.0-beta.7
Category
Value sources
Since
1.0.0
Member of
Fx

Follow one execution

Evaluate the source factory lazily for each run; then forward its selected source.

Fx timelinesuspend(chooseSource)suspend
Operatorsuspend(chooseSource)
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.

fx is not evaluated during construction. It is evaluated once per run inside Effect.suspend; thrown exceptions become Effect defects, and the returned producer is owned and interrupted as part of that same run.

Source implementation · Learn the surrounding model

Compare all Fx timelines →

Import

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

Access Fx.suspend 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 suspend: <A, E, R>(fx: () => Fx<A, E, R>) => Fx<A, E, R>;

Why

Recursive producers and producers whose definition depends on fresh mutable state need laziness at the Fx boundary, not merely laziness of a value emission.

Ownership and lifetime

fx is not evaluated during construction. It is evaluated once per run inside Effect.suspend; thrown exceptions become Effect defects, and the returned producer is owned and interrupted as part of that same run.

Examples

import { collectAll, succeed, suspend } from "@typed/fx/Fx"

let next = 0
const source = suspend(() => succeed(++next))
const firstRun = collectAll(source)
const secondRun = collectAll(source)

Other public imports

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

Source