effect-io-ai

Package: effect
Module: Effect

Effect.whenEffect

Conditionally executes an effect based on the result of another effect.

Details

This function allows you to run an effect only if a conditional effect evaluating to a boolean resolves to true. If the conditional effect evaluates to true, the specified effect is executed, and its result is wrapped in Option.some. If the conditional effect evaluates to false, the effect is skipped, and the result is Option.none.

When to Use

This function is particularly useful when the decision to execute an effect depends on the result of another effect, such as a random value, a user-provided input, or a network request result.

Example (Using an Effect as a Condition)

import { Effect, Random } from "effect"

const randomIntOption = Random.nextInt.pipe(
  Effect.whenEffect(Random.nextBoolean)
)

console.log(Effect.runSync(randomIntOption))
// Example Output:
// { _id: 'Option', _tag: 'Some', value: 8609104974198840 }

See

• when for a version that allows the condition to be a boolean.
• unlessEffect for a version that executes the effect when the condition is false.

Signature

declare const whenEffect: { <E, R>(condition: Effect<boolean, E, R>): <A, E2, R2>(effect: Effect<A, E2, R2>) => Effect<Option.Option<A>, E | E2, R | R2>; <A, E2, R2, E, R>(self: Effect<A, E2, R2>, condition: Effect<boolean, E, R>): Effect<Option.Option<A>, E2 | E, R2 | R>; }

Source

Since v2.0.0