<E, B, A, C = B>(options: {
readonly onFailure: (error: E) => B
readonly onSuccess: (ok: A) => C
}): (self: Result<A, E>) => B | C
<A, E, B, C = B>(
self: Result<A, E>,
options: {
readonly onFailure: (error: E) => B
readonly onSuccess: (ok: A) => C
}
): B | CFolds a Result into a single value by applying one of two functions.
When to use
Use when a Result's success and failure branches should be collapsed into
one plain output type.
Details
- Applies
onSuccessif the result is aSuccess - Applies
onFailureif the result is aFailure - Both branches must return the same type (or a common supertype)
Example (Folding to a string)
import { pipe, Result } from "effect"
const format = Result.match({
onSuccess: (n: number) => `Got ${n}`,
onFailure: (e: string) => `Err: ${e}`
})
console.log(format(Result.succeed(42)))
// Output: "Got 42"
console.log(format(Result.fail("timeout")))
// Output: "Err: timeout"Source effect/Result.ts:90516 lines
export const const match: {
<E, B, A, C = B>(options: {
readonly onFailure: (error: E) => B
readonly onSuccess: (ok: A) => C
}): (self: Result<A, E>) => B | C
<A, E, B, C = B>(
self: Result<A, E>,
options: {
readonly onFailure: (error: E) => B
readonly onSuccess: (ok: A) => C
}
): B | C
}
Folds a Result into a single value by applying one of two functions.
When to use
Use when a Result's success and failure branches should be collapsed into
one plain output type.
Details
- Applies
onSuccess if the result is a Success
- Applies
onFailure if the result is a Failure
- Both branches must return the same type (or a common supertype)
Example (Folding to a string)
import { pipe, Result } from "effect"
const format = Result.match({
onSuccess: (n: number) => `Got ${n}`,
onFailure: (e: string) => `Err: ${e}`
})
console.log(format(Result.succeed(42)))
// Output: "Got 42"
console.log(format(Result.fail("timeout")))
// Output: "Err: timeout"
match: {
<function (type parameter) E in <E, B, A, C = B>(options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): (self: Result<A, E>) => B | C
function (type parameter) B in <E, B, A, C = B>(options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): (self: Result<A, E>) => B | C
function (type parameter) A in <E, B, A, C = B>(options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): (self: Result<A, E>) => B | C
function (type parameter) C in <E, B, A, C = B>(options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): (self: Result<A, E>) => B | C
function (type parameter) B in <E, B, A, C = B>(options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): (self: Result<A, E>) => B | C
options: {
readonly onFailure: (error: E) => B
readonly onSuccess: (ok: A) => C
}
onFailure: (error: E) => BonFailure: (error: Eerror: function (type parameter) E in <E, B, A, C = B>(options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): (self: Result<A, E>) => B | C
function (type parameter) B in <E, B, A, C = B>(options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): (self: Result<A, E>) => B | C
onSuccess: (ok: A) => ConSuccess: (ok: Aok: function (type parameter) A in <E, B, A, C = B>(options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): (self: Result<A, E>) => B | C
function (type parameter) C in <E, B, A, C = B>(options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): (self: Result<A, E>) => B | C
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 <E, B, A, C = B>(options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): (self: Result<A, E>) => B | C
function (type parameter) E in <E, B, A, C = B>(options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): (self: Result<A, E>) => B | C
function (type parameter) B in <E, B, A, C = B>(options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): (self: Result<A, E>) => B | C
function (type parameter) C in <E, B, A, C = B>(options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): (self: Result<A, E>) => B | C
function (type parameter) A in <A, E, B, C = B>(self: Result<A, E>, options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
function (type parameter) E in <A, E, B, C = B>(self: Result<A, E>, options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
function (type parameter) B in <A, E, B, C = B>(self: Result<A, E>, options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
function (type parameter) C in <A, E, B, C = B>(self: Result<A, E>, options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
function (type parameter) B in <A, E, B, C = B>(self: Result<A, E>, options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
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, B, C = B>(self: Result<A, E>, options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
function (type parameter) E in <A, E, B, C = B>(self: Result<A, E>, options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
options: {
readonly onFailure: (error: E) => B
readonly onSuccess: (ok: A) => C
}
onFailure: (error: E) => BonFailure: (error: Eerror: function (type parameter) E in <A, E, B, C = B>(self: Result<A, E>, options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
function (type parameter) B in <A, E, B, C = B>(self: Result<A, E>, options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
onSuccess: (ok: A) => ConSuccess: (ok: Aok: function (type parameter) A in <A, E, B, C = B>(self: Result<A, E>, options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
function (type parameter) C in <A, E, B, C = B>(self: Result<A, E>, options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
function (type parameter) B in <A, E, B, C = B>(self: Result<A, E>, options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
function (type parameter) C in <A, E, B, C = B>(self: Result<A, E>, options: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
import dualdual(
2,
<function (type parameter) A in <A, E, B, C = B>(self: Result<A, E>, { onFailure, onSuccess }: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
function (type parameter) E in <A, E, B, C = B>(self: Result<A, E>, { onFailure, onSuccess }: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
function (type parameter) B in <A, E, B, C = B>(self: Result<A, E>, { onFailure, onSuccess }: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
function (type parameter) C in <A, E, B, C = B>(self: Result<A, E>, { onFailure, onSuccess }: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
function (type parameter) B in <A, E, B, C = B>(self: Result<A, E>, { onFailure, onSuccess }: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
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, B, C = B>(self: Result<A, E>, { onFailure, onSuccess }: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
function (type parameter) E in <A, E, B, C = B>(self: Result<A, E>, { onFailure, onSuccess }: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
onFailure: (error: E) => BonFailure, onSuccess: (ok: A) => ConSuccess }: {
readonly onFailure: (error: E) => BonFailure: (error: Eerror: function (type parameter) E in <A, E, B, C = B>(self: Result<A, E>, { onFailure, onSuccess }: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
function (type parameter) B in <A, E, B, C = B>(self: Result<A, E>, { onFailure, onSuccess }: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
onSuccess: (ok: A) => ConSuccess: (ok: Aok: function (type parameter) A in <A, E, B, C = B>(self: Result<A, E>, { onFailure, onSuccess }: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
function (type parameter) C in <A, E, B, C = B>(self: Result<A, E>, { onFailure, onSuccess }: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
function (type parameter) B in <A, E, B, C = B>(self: Result<A, E>, { onFailure, onSuccess }: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
function (type parameter) C in <A, E, B, C = B>(self: Result<A, E>, { onFailure, onSuccess }: {
readonly onFailure: (error: E) => B;
readonly onSuccess: (ok: A) => C;
}): B | C
const isFailure: <A, E>(
self: Result<A, E>
) => self is Failure<A, E>
Checks whether a Result is a Failure.
When to use
Use to narrow a known Result to the Failure variant.
Details
- Acts as a TypeScript type guard, narrowing to
Failure<A, E>
- After narrowing, you can access
.failure to read the error value
Example (Narrowing to failure)
import { Result } from "effect"
const result = Result.fail("oops")
if (Result.isFailure(result)) {
console.log(result.failure)
// Output: "oops"
}
isFailure(self: Result<A, E>self) ? onFailure: (error: E) => BonFailure(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) : onSuccess: (ok: A) => ConSuccess(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)
)Referenced by 9 symbols