<E>(onFailure: (err: E) => unknown): <A>(self: Result<A, E>) => A
<A, E>(self: Result<A, E>, onFailure: (err: E) => unknown): AExtracts the success value or throws a custom error derived from the failure.
When to use
Use when converting a Result into a thrown exception with a custom error
message or error type.
Details
Success<A>returnsAFailure<E>throws the value returned byonFailure(e)
Example (Throwing a custom error)
import { Result } from "effect"
console.log(
Result.getOrThrowWith(Result.succeed(1), () => new Error("fail"))
)
// Output: 1
// This would throw: new Error("Unexpected: oops")
// Result.getOrThrowWith(
// Result.fail("oops"),
// (err) => new Error(`Unexpected: ${err}`)
// )export const const getOrThrowWith: {
<E>(onFailure: (err: E) => unknown): <A>(
self: Result<A, E>
) => A
<A, E>(
self: Result<A, E>,
onFailure: (err: E) => unknown
): A
}
Extracts the success value or throws a custom error derived from the failure.
When to use
Use when converting a Result into a thrown exception with a custom error
message or error type.
Details
Success<A> returns AFailure<E> throws the value returned by onFailure(e)
Example (Throwing a custom error)
import { Result } from "effect"
console.log(
Result.getOrThrowWith(Result.succeed(1), () => new Error("fail"))
)
// Output: 1
// This would throw: new Error("Unexpected: oops")
// Result.getOrThrowWith(
// Result.fail("oops"),
// (err) => new Error(`Unexpected: ${err}`)
// )
getOrThrowWith: {
<function (type parameter) E in <E>(onFailure: (err: E) => unknown): <A>(self: Result<A, E>) => AE>(onFailure: (err: E) => unknownonFailure: (err: Eerr: function (type parameter) E in <E>(onFailure: (err: E) => unknown): <A>(self: Result<A, E>) => AE) => unknown): <function (type parameter) A in <A>(self: Result<A, E>): AA>(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>(self: Result<A, E>): AA, function (type parameter) E in <E>(onFailure: (err: E) => unknown): <A>(self: Result<A, E>) => AE>) => function (type parameter) A in <A>(self: Result<A, E>): AA
<function (type parameter) A in <A, E>(self: Result<A, E>, onFailure: (err: E) => unknown): AA, function (type parameter) E in <A, E>(self: Result<A, E>, onFailure: (err: E) => unknown): AE>(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>, onFailure: (err: E) => unknown): AA, function (type parameter) E in <A, E>(self: Result<A, E>, onFailure: (err: E) => unknown): AE>, onFailure: (err: E) => unknownonFailure: (err: Eerr: function (type parameter) E in <A, E>(self: Result<A, E>, onFailure: (err: E) => unknown): AE) => unknown): function (type parameter) A in <A, E>(self: Result<A, E>, onFailure: (err: E) => unknown): AA
} = import dualdual(2, <function (type parameter) A in <A, E>(self: Result<A, E>, onFailure: (err: E) => unknown): AA, function (type parameter) E in <A, E>(self: Result<A, E>, onFailure: (err: E) => unknown): AE>(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>, onFailure: (err: E) => unknown): AA, function (type parameter) E in <A, E>(self: Result<A, E>, onFailure: (err: E) => unknown): AE>, onFailure: (err: E) => unknownonFailure: (err: Eerr: function (type parameter) E in <A, E>(self: Result<A, E>, onFailure: (err: E) => unknown): AE) => unknown): function (type parameter) A in <A, E>(self: Result<A, E>, onFailure: (err: E) => unknown): AA => {
if (const isSuccess: <A, E>(
self: Result<A, E>
) => self is Success<A, E>
Checks whether a Result is a Success.
When to use
Use to narrow a known Result to the Success variant.
Details
- Acts as a TypeScript type guard, narrowing to
Success<A, E>
- After narrowing, you can access
.success to read the value
Example (Narrowing to success)
import { Result } from "effect"
const result = Result.succeed(42)
if (Result.isSuccess(result)) {
console.log(result.success)
// Output: 42
}
isSuccess(self: Result<A, E>self)) {
return self: Result<A, E>(parameter) self: {
_tag: "Success";
_op: "Success";
success: A;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
Success<A, E>.success: Asuccess
}
throw onFailure: (err: E) => unknownonFailure(self: Result<A, E>(parameter) self: {
_tag: "Failure";
_op: "Failure";
failure: E;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
Failure<A, E>.failure: Efailure)
})