<A, E>(self: Result<A, E>): Option<E>Extracts the failure value as an Option, discarding the success.
When to use
Use when you need to extract the failure value from a Result as an
Option and discard successful values.
Details
Failure<E>becomesSome<E>Success<A>becomesNone
Example (Extracting the failure as an Option)
import { Option, Result } from "effect"
console.log(Result.getFailure(Result.succeed("ok")))
// Output: { _tag: "None" }
console.log(Result.getFailure(Result.fail("err")))
// Output: { _tag: "Some", value: "err" }export const const getFailure: <A, E>(
self: Result<A, E>
) => Option<E>
Extracts the failure value as an Option, discarding the success.
When to use
Use when you need to extract the failure value from a Result as an
Option and discard successful values.
Details
Failure<E> becomes Some<E>Success<A> becomes None
Example (Extracting the failure as an Option)
import { Option, Result } from "effect"
console.log(Result.getFailure(Result.succeed("ok")))
// Output: { _tag: "None" }
console.log(Result.getFailure(Result.fail("err")))
// Output: { _tag: "Some", value: "err" }
getFailure: <function (type parameter) A in <A, E>(self: Result<A, E>): Option<E>A, function (type parameter) E in <A, E>(self: Result<A, E>): Option<E>E>(self: Result<A, E>self: type Result<A, E = never> = Success<A, E> | Failure<A, E>A value that is either Success<A, E> or Failure<A, E>.
When to use
Use when both success and failure should remain available as data and
Option would lose failure information.
Details
- Use
succeed
/
fail
to construct
- Use
match
to fold both branches
- Use
isSuccess
/
isFailure
to narrow the type
E defaults to never, so Result<number> means a result that cannot fail.
Example (Creating and matching a Result)
import { Result } from "effect"
const success = Result.succeed(42)
const failure = Result.fail("something went wrong")
const message = Result.match(success, {
onSuccess: (value) => `Success: ${value}`,
onFailure: (error) => `Error: ${error}`
})
console.log(message)
// Output: "Success: 42"
Namespace containing type-level utilities for extracting the inner types
of a Result.
Example (Extracting inner types)
import type { Result } from "effect"
type R = Result.Result<number, string>
// number
type A = Result.Result.Success<R>
// string
type E = Result.Result.Failure<R>
Result<function (type parameter) A in <A, E>(self: Result<A, E>): Option<E>A, function (type parameter) E in <A, E>(self: Result<A, E>): Option<E>E>) => import OptionOption<function (type parameter) E in <A, E>(self: Result<A, E>): Option<E>E> = import resultresult.const getFailure: <A, E>(
self: Result.Result<A, E>
) => Option<E>