effect-io-ai

Package: effect
Module: Match

Match.result

Wraps the match result in a Result, distinguishing matched and unmatched cases.

Details

This function ensures that the result of a matcher is always wrapped in an Result, allowing clear differentiation between successful matches (Ok(value)) and cases where no pattern matched (Err(unmatched value)).

This approach is particularly useful when handling optional values or when an unmatched case should be explicitly handled rather than returning a default value or throwing an error.

Example (Extracting a user role with Match.result)

import { Match } from "effect"

type User = { readonly role: "admin" | "editor" | "viewer" }

// Create a matcher to extract user roles
const getRole = Match.type<User>().pipe(
  Match.when({ role: "admin" }, () => "Has full access"),
  Match.when({ role: "editor" }, () => "Can edit content"),
  Match.result // Wrap the result in an Result
)

console.log(getRole({ role: "admin" }))
// Output: { _id: 'Result', _tag: 'Ok', ok: 'Has full access' }

console.log(getRole({ role: "viewer" }))
// Output: { _id: 'Result', _tag: 'Err', err: { role: 'viewer' } }

Signature

declare const result: <I, F, R, A, Pr, Ret>(self: Matcher<I, F, R, A, Pr, Ret>) => [Pr] extends [never] ? (input: I) => Result.Result<Unify<A>, R> : Result.Result<Unify<A>, R>

Source

Since v4.0.0