SubscriptionRef.modifyEffect — API

SubscriptionRef.modifyEffectconsteffect/SubscriptionRef.ts:504

<B, A, E, R>(modify: (a: A) => Effect.Effect<readonly [B, A], E, R>): (
  self: SubscriptionRef<A>
) => Effect.Effect<B, E, R>
<A, B, E, R>(
  self: SubscriptionRef<A>,
  modify: (a: A) => Effect.Effect<readonly [B, A], E, R>
): Effect.Effect<B, E, R>

Modifies the SubscriptionRef atomically with an effectful function that computes a return value and a new value, notifying subscribers of the change.

Example (Modifying with an effect)

import { Effect, SubscriptionRef } from "effect"

const program = Effect.gen(function*() {
  const ref = yield* SubscriptionRef.make(10)

  const result = yield* SubscriptionRef.modifyEffect(
    ref,
    (n) => Effect.succeed([`Doubled from ${n}`, n * 2] as const)
  )
  console.log(result)

  const newValue = yield* SubscriptionRef.get(ref)
  console.log("New value:", newValue)
})

modifications

Source effect/SubscriptionRef.ts:50418 lines

export const modifyEffect: {
  <B, A, E, R>(
    modify: (a: A) => Effect.Effect<readonly [B, A], E, R>
  ): (self: SubscriptionRef<A>) => Effect.Effect<B, E, R>
  <A, B, E, R>(
    self: SubscriptionRef<A>,
    modify: (a: A) => Effect.Effect<readonly [B, A], E, R>
  ): Effect.Effect<B, E, R>
} = dual(2, <A, B, E, R>(
  self: SubscriptionRef<A>,
  modify: (a: A) => Effect.Effect<readonly [B, A], E, R>
): Effect.Effect<B, E, R> =>
  self.semaphore.withPermit(Effect.suspend(() =>
    Effect.map(modify(self.value), ([b, newValue]) => {
      setUnsafe(self, newValue)
      return b
    })
  )))