Import
import { RefSubject } from "@typed/fx";Access RefSubject.mapEffect through the imported RefSubject 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 mapEffect: {
<T extends RefSubject.Any | Computed.Any | Filtered.Any, B, E2, R2>(f: (a: Success<T>) => Effect.Effect<B, E2, R2>): (ref: T) => T extends Filtered.Any ? Filtered<B, Error<T> | E2, Services<T> | R2> : Computed<B, Error<T> | E2, Services<T> | R2>;
<A, E, R, B, E2, R2>(ref: RefSubject<A, E, R> | Computed<A, E, R>, f: (a: A) => Effect.Effect<B, E2, R2>): Computed<B, E | E2, R | R2>;
<A, E, R, B, E2, R2>(ref: Filtered<A, E, R>, f: (a: A) => Effect.Effect<B, E2, R2>): Filtered<B, E | E2, R | R2>;
<R0, E0, A, E, R, E2, R2, C, E3, R3>(versioned: Versioned.Versioned<R0, E0, A, E, R, A, E2, R2>, f: (a: A) => Effect.Effect<C, E3, R3>): Computed<C, E0 | E | E2 | E3, R0 | R2 | R3 | Exclude<R, Scope.Scope>>;
};Why
Applies one Effectful derivation to current reads and pushed versions. RefSubject and Computed
inputs return Computed and add only E2; a Filtered input returns Filtered and preserves its
conditional absence in addition to E2.
Ownership and lifetime
No callback runs until the result is read or observed. Computed results cannot become absent and
do not add NoSuchElementError; only the Filtered overload can fail a current read for absence.
Callback services and failures remain R2 and E2, and the observing Scope owns subscription
cleanup.
Examples
import { Effect } from "effect"
import * as RefSubject from "@typed/fx/RefSubject"
const program = Effect.gen(function* () {
const count = yield* RefSubject.make(5)
// Transform with an async operation
const doubled = RefSubject.mapEffect(count, (n) =>
Effect.succeed(n * 2)
)
const value = yield* doubled
console.log(value) // 10
// Update source
yield* RefSubject.set(count, 7)
// Computed automatically updates
const newValue = yield* doubled
console.log(newValue) // 14
})Other public imports
These import paths expose the same declaration. Each page retains its own public name and signature.