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True Myth / result / Err

Interface: Err<T, E> ​

An Err instance is the failure variant instance of the Result type, representing a failure outcome from an operation which may fail. For a full discussion, see the module docs.

Extends ​

  • Omit<ResultImpl<T, E>, "value" | "cast">

Type Parameters ​

T ​

T

The type which would be wrapped in an Ok variant of Result.

E ​

E

The type wrapped in this Err variant of Result.

Properties ​

error ​

error: E

The wrapped error value.

Overrides ​

Omit.error

isErr ​

isErr: true

Is the Result an Err?

Overrides ​

Omit.isErr

isOk ​

isOk: false

Is the Result an Ok?

Overrides ​

Omit.isOk

variant ​

readonly variant: "Err"

Err is always Variant.Err.

Overrides ​

Omit.variant

Methods ​

and() ​

and<U>(mAnd): Result<U, E>

Method variant for and

Type Parameters ​

U ​

U

Parameters ​

mAnd ​

Result<U, E>

Returns ​

Result<U, E>

Inherited from ​

Omit.and

andThen() ​

Call Signature ​

andThen<U>(andThenFn): Result<U, E>

Method variant for andThen

Type Parameters ​
U ​

U

Parameters ​
andThenFn ​

(t) => Result<U, E>

Returns ​

Result<U, E>

Inherited from ​

Omit.andThen

Call Signature ​

andThen<R>(andThenFn): Result<OkFor<R>, E | ErrFor<R>>

Method variant for andThen

Type Parameters ​
R ​

R extends AnyResult

Parameters ​
andThenFn ​

(t) => R

Returns ​

Result<OkFor<R>, E | ErrFor<R>>

Inherited from ​

Omit.andThen

ap() ​

ap<A, B>(this, r): Result<B, E>

Method variant for ap

Type Parameters ​

A ​

A

B ​

B

Parameters ​

this ​

Result<(a) => B, E>

r ​

Result<A, E>

Returns ​

Result<B, E>

Inherited from ​

Omit.ap

cast() ​

cast<U>(): Result<U, E>

Type Parameters ​

U ​

U

Returns ​

Result<U, E>

equals() ​

equals(comparison): boolean

Method variant for equals

Parameters ​

comparison ​

Result<T, E>

Returns ​

boolean

Inherited from ​

Omit.equals

flatten() ​

flatten<A, F>(this): Result<A, E | F>

Given a nested Result, remove one layer of nesting.

For example, given a Result<Result<string, E2>, E1>, the resulting type after using this method will be Result<string, E1 | E2>.

Note ​

This method only works when the value wrapped in Result is another Result. If you have a Result<string, E> or Result<number, E>, this method won't work. If you have a Result<Result<string, E2>, E1>, then you can call .flatten() to get back a Result<string, E1 | E2>.

Examples ​

ts
import * as result from 'true-myth/result';

const nested = result.ok(result.ok('hello'));
const flattened = nested.flatten(); // Result<string, never>
console.log(flattened); // Ok('hello')

const nestedError = result.ok(result.err('inner error'));
const flattenedError = nestedError.flatten(); // Result<never, string>
console.log(flattenedError); // Err('inner error')

const errorNested = result.err<Result<string, string>, string>('outer error');
const flattenedOuter = errorNested.flatten(); // Result<string, string>
console.log(flattenedOuter); // Err('outer error')

Type Parameters ​

A ​

A

F ​

F

Parameters ​

this ​

Result<Result<A, F>, E>

Returns ​

Result<A, E | F>

Inherited from ​

Omit.flatten

map() ​

map<U>(mapFn): Result<U, E>

Method variant for map

Type Parameters ​

U ​

U

Parameters ​

mapFn ​

(t) => U

Returns ​

Result<U, E>

Inherited from ​

Omit.map

mapErr() ​

mapErr<F>(mapErrFn): Result<T, F>

Method variant for mapErr

Type Parameters ​

F ​

F

Parameters ​

mapErrFn ​

(e) => F

Returns ​

Result<T, F>

Inherited from ​

Omit.mapErr

mapOr() ​

mapOr<U>(orU, mapFn): U

Method variant for mapOr

Type Parameters ​

U ​

U

Parameters ​

orU ​

U

mapFn ​

(t) => U

Returns ​

U

Inherited from ​

Omit.mapOr

mapOrElse() ​

mapOrElse<U>(orElseFn, mapFn): U

Method variant for mapOrElse

Type Parameters ​

U ​

U

Parameters ​

orElseFn ​

(err) => U

mapFn ​

(t) => U

Returns ​

U

Inherited from ​

Omit.mapOrElse

match() ​

match<A>(matcher): A

Method variant for match

Type Parameters ​

A ​

A

Parameters ​

matcher ​

Matcher<T, E, A>

Returns ​

A

Inherited from ​

Omit.match

or() ​

or<F>(orResult): Result<T, F>

Method variant for or

Type Parameters ​

F ​

F

Parameters ​

orResult ​

Result<T, F>

Returns ​

Result<T, F>

Inherited from ​

Omit.or

orElse() ​

Call Signature ​

orElse<F>(orElseFn): Result<T, F>

Method variant for orElse

Type Parameters ​
F ​

F

Parameters ​
orElseFn ​

(err) => Result<T, F>

Returns ​

Result<T, F>

Inherited from ​

Omit.orElse

Call Signature ​

orElse<R>(orElseFn): Result<T | OkFor<R>, ErrFor<R>>

Method variant for orElse

Type Parameters ​
R ​

R extends AnyResult

Parameters ​
orElseFn ​

(err) => R

Returns ​

Result<T | OkFor<R>, ErrFor<R>>

Inherited from ​

Omit.orElse

toJSON() ​

toJSON(): Serialized<T, E>

Method variant for toJSON

Returns ​

Serialized<T, E>

Inherited from ​

Omit.toJSON

toString() ​

toString(): string

Method variant for toString

Returns ​

string

Inherited from ​

Omit.toString

unwrapOr() ​

unwrapOr<U>(defaultValue): T | U

Method variant for unwrapOr

Type Parameters ​

U ​

U = T

Parameters ​

defaultValue ​

U

Returns ​

T | U

Inherited from ​

Omit.unwrapOr

unwrapOrElse() ​

unwrapOrElse<U>(elseFn): T | U

Method variant for unwrapOrElse

Type Parameters ​

U ​

U

Parameters ​

elseFn ​

(error) => U

Returns ​

T | U

Inherited from ​

Omit.unwrapOrElse