effect-io-ai

Package: effect
Module: Ref

Ref.getAndUpdate

Gets the current value of the Ref, updates it with the given function, and returns the previous value atomically.

When to use

Use to derive a new Ref value while returning the previous value.

Example (Updating and returning the previous value)

import { Effect, Ref } from "effect"

const program = Effect.gen(function*() {
  const counter = yield* Ref.make(10)

  // Get current value and update it atomically
  const previous = yield* Ref.getAndUpdate(counter, (n) => n * 2)
  console.log(previous) // 10

  const current = yield* Ref.get(counter)
  console.log(current) // 20
})

See

• update for updating without returning the previous value
• updateAndGet for returning the new value instead

Signature

declare const getAndUpdate: (<A>(f: (a: A) => A) => (self: Ref<A>) => Effect.Effect<A>) & (<A>(self: Ref<A>, f: (a: A) => A) => Effect.Effect<A>)

Source

Since v2.0.0