effect-io-ai

Package: effect
Module: Effect

Effect.matchEffect

Handles both success and failure by running effectful handlers.

When to use

Use when you need to handle an Effect’s failure or success with handlers that return effects.

Details

Use matchEffect when either branch needs to return an Effect, such as performing logging, recovery, notification, or other effectful work. The returned effect succeeds or fails according to the handler that is run.

Example (Matching success and failure with effectful handlers)

import { Data, Effect } from "effect"

class ExampleError extends Data.TaggedError("ExampleError")<{ readonly message: string }> {}

const success: Effect.Effect<number, ExampleError> = Effect.succeed(42)
const failure: Effect.Effect<number, ExampleError> = Effect.fail(
  new ExampleError({ message: "Uh oh!" })
)

const program1 = Effect.matchEffect(success, {
  onFailure: (error) =>
    Effect.succeed(`failure: ${error.message}`).pipe(
      Effect.tap(Effect.log)
    ),
  onSuccess: (value) =>
    Effect.succeed(`success: ${value}`).pipe(Effect.tap(Effect.log))
})

console.log(Effect.runSync(program1))
// Output:
// timestamp=... level=INFO fiber=#0 message="success: 42"
// success: 42

const program2 = Effect.matchEffect(failure, {
  onFailure: (error) =>
    Effect.succeed(`failure: ${error.message}`).pipe(
      Effect.tap(Effect.log)
    ),
  onSuccess: (value) =>
    Effect.succeed(`success: ${value}`).pipe(Effect.tap(Effect.log))
})

console.log(Effect.runSync(program2))
// Output:
// timestamp=... level=INFO fiber=#1 message="failure: Uh oh!"
// failure: Uh oh!

See

• match if you don’t need side effects and only want to handle the result or failure.

Signature

declare const matchEffect: { <E, A2, E2, R2, A, A3, E3, R3>(options: { readonly onFailure: (e: E) => Effect<A2, E2, R2>; readonly onSuccess: (a: A) => Effect<A3, E3, R3>; }): <R>(self: Effect<A, E, R>) => Effect<A2 | A3, E2 | E3, R2 | R3 | R>; <A, E, R, A2, E2, R2, A3, E3, R3>(self: Effect<A, E, R>, options: { readonly onFailure: (e: E) => Effect<A2, E2, R2>; readonly onSuccess: (a: A) => Effect<A3, E3, R3>; }): Effect<A2 | A3, E2 | E3, R2 | R3 | R>; }

Source

Since v2.0.0