effect-io-ai

Package: effect
Module: Effect

Effect.match

Handles both success and failure cases of an effect without performing side effects.

When to use

Use when you need to fold an Effect into a value by handling success and failure differently without triggering side effects.

Details

match lets you define custom handlers for both success and failure scenarios. You provide separate functions to handle each case, allowing you to process the result if the effect succeeds, or handle the error if the effect fails.

Example (Matching success and failure values)

import { Data, Effect } from "effect"

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

const success: Effect.Effect<number, ExampleError> = Effect.succeed(42)

const program1 = Effect.match(success, {
  onFailure: (error) => `failure: ${error.message}`,
  onSuccess: (value) => `success: ${value}`
})

// Run and log the result of the successful effect
Effect.runPromise(program1).then(console.log)
// Output: "success: 42"

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

const program2 = Effect.match(failure, {
  onFailure: (error) => `failure: ${error.message}`,
  onSuccess: (value) => `success: ${value}`
})

// Run and log the result of the failed effect
Effect.runPromise(program2).then(console.log)
// Output: "failure: Uh oh!"

See

• matchEffect if you need to perform side effects in the handlers.

Signature

declare const match: { <E, A2, A, A3>(options: { readonly onFailure: (error: E) => A2; readonly onSuccess: (value: A) => A3; }): <R>(self: Effect<A, E, R>) => Effect<A2 | A3, never, R>; <A, E, R, A2, A3>(self: Effect<A, E, R>, options: { readonly onFailure: (error: E) => A2; readonly onSuccess: (value: A) => A3; }): Effect<A2 | A3, never, R>; }

Source

Since v2.0.0