Err | true-myth

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.

Type parameters

T

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

The type wrapped in this Err variant of Result.

Hierarchy

Implements

ResultShape<T, E>

Index

Constructors

constructor

Properties

Methods

Constructors

constructor

new Err(error: E | null): Err

- Defined in result.ts:333
Create an instance of Result.Err with new.

Note: While you may create the Result type via normal JavaScript class construction, it is not recommended for the functional style for which the library is intended. Instead, use Result.err.
```
// Avoid:
const anErr = new Result.Err('alas, failure');

// Prefer:
const anErr = Result.err('alas, failure');
```
Note that you may explicitly pass Unit to the Err constructor to create a Result<T, Unit>. However, you may not call the Err constructor with null or undefined to get that result (the type system won't allow you to construct it that way). Instead, for convenience, you can simply call Result.err(), which will construct the type correctly.

throws

If you pass null or undefined.
Parameters
- error: E | null
 
 The value to wrap in a Result.Err.
 
 Note: null and undefined are allowed by the type signature so that the constructor may throw on those rather than constructing a type like Result<number, undefined>.
Returns Err

Properties

error

error: E

The wrapped error value.

variant

variant: Err = Variant.Err

Err is always Variant.Err.

Methods

and

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

Implementation of ResultShape.and
- Defined in result.ts:423
Method variant for Result.and

Type parameters
- U
Parameters
- this: Result<T, E>
- mAnd: Result<U, E>
Returns Result<U, E>

andThen

andThen(this: Result<T, E>, andThenFn: function): Result<U, E>

- Defined in result.ts:428
Method variant for Result.andThen

Type parameters
- U
Parameters
- this: Result<T, E>
- andThenFn: function
 - - (t: T): Result<U, E>
 - Parameters
 - t: T
 Returns Result<U, E>
Returns Result<U, E>

ap

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

Implementation of ResultShape.ap
- Defined in result.ts:483
Method variant for Result.ap

Type parameters
- A
- B
Parameters
- this: Result<function, E>
- r: Result<A, E>
Returns Result<B, E>

chain

chain(this: Result<T, E>, chainFn: function): Result<U, E>

- Defined in result.ts:433
Method variant for Result.chain

Type parameters
- U
Parameters
- this: Result<T, E>
- chainFn: function
 - - (t: T): Result<U, E>
 - Parameters
 - t: T
 Returns Result<U, E>
Returns Result<U, E>

equals

equals(this: Result<T, E>, comparison: Result<T, E>): boolean

Implementation of ResultShape.equals
- Defined in result.ts:478
Method variant for Result.equals

Parameters
- this: Result<T, E>
- comparison: Result<T, E>
Returns boolean

flatMap

flatMap(this: Result<T, E>, flatMapFn: function): Result<U, E>

- Defined in result.ts:438
Method variant for Result.flatMap

Type parameters
- U
Parameters
- this: Result<T, E>
- flatMapFn: function
 - - (t: T): Result<U, E>
 - Parameters
 - t: T
 Returns Result<U, E>
Returns Result<U, E>

isErr

isErr(this: Result<T, E>): this is Err<T, E>

Implementation of ResultShape.isErr
- Defined in result.ts:383
Method variant for Result.isErr

Parameters
- this: Result<T, E>
Returns this is Err<T, E>

isOk

isOk(this: Result<T, E>): this is Ok<T, E>

Implementation of ResultShape.isOk
- Defined in result.ts:378
Method variant for Result.isOk

Parameters
- this: Result<T, E>
Returns this is Ok<T, E>

map

map(this: Result<T, E>, mapFn: function): Result<U, E>

- Defined in result.ts:388
Method variant for Result.map

Type parameters
- U
Parameters
- this: Result<T, E>
- mapFn: function
 - - (t: T): U
 - Parameters
 - t: T
 Returns U
Returns Result<U, E>

mapErr

mapErr<F>(this: Result<T, E>, mapErrFn: function): Result<T, F>

- Defined in result.ts:408
Method variant for Result.mapErr

Type parameters
- F
Parameters
- this: Result<T, E>
- mapErrFn: function
 - - (e: E): F
 - Parameters
 - e: E
 Returns F
Returns Result<T, F>

mapOr

mapOr(this: Result<T, E>, orU: U, mapFn: function): U

- Defined in result.ts:393
Method variant for Result.mapOr

Type parameters
- U
Parameters
- this: Result<T, E>
- orU: U
- mapFn: function
 - - (t: T): U
 - Parameters
 - t: T
 Returns U
Returns U

mapOrElse

mapOrElse(this: Result<T, E>, orElseFn: function, mapFn: function): U

- Defined in result.ts:398
Method variant for Result.mapOrElse

Type parameters
- U
Parameters
- this: Result<T, E>
- orElseFn: function
 - - (err: E): U
 - Parameters
 - err: E
 Returns U
- mapFn: function
 - - (t: T): U
 - Parameters
 - t: T
 Returns U
Returns U

match

match(this: Result<T, E>, matchObj: Matcher<T, E, U>): U

Implementation of ResultShape.match
- Defined in result.ts:403
Method variant for Result.match

Type parameters
- U
Parameters
- this: Result<T, E>
- matchObj: Matcher<T, E, U>
Returns U

or

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

Implementation of ResultShape.or
- Defined in result.ts:413
Method variant for Result.or

Type parameters
- F
Parameters
- this: Result<T, E>
- orResult: Result<T, F>
Returns Result<T, F>

orElse

orElse<F>(this: Result<T, E>, orElseFn: function): Result<T, F>

- Defined in result.ts:418
Method variant for Result.orElse

Type parameters
- F
Parameters
- this: Result<T, E>
- orElseFn: function
 - - (err: E): Result<T, F>
 - Parameters
 - err: E
 Returns Result<T, F>
Returns Result<T, F>

toJSON

toJSON(this: Result<T, E>): ResultJSON<T, E>

Implementation of ResultShape.toJSON
- Defined in result.ts:473
Method variant for Result.toJSON

Parameters
- this: Result<T, E>
Returns ResultJSON<T, E>

toMaybe

toMaybe(this: Result<T, E>): Maybe<T>

Implementation of ResultShape.toMaybe
- Defined in result.ts:463
Method variant for Result.toMaybe

Parameters
- this: Result<T, E>
Returns Maybe<T>

toString

toString(this: Result<T, E>): string

Implementation of ResultShape.toString
- Defined in result.ts:468
Method variant for Result.toString

Parameters
- this: Result<T, E>
Returns string

unsafelyUnwrap

unsafelyUnwrap(): never

Implementation of ResultShape.unsafelyUnwrap
- Defined in result.ts:443
Method variant for Result.unsafelyUnwrap

Returns never

unsafelyUnwrapErr

unsafelyUnwrapErr(): E

Implementation of ResultShape.unsafelyUnwrapErr
- Defined in result.ts:448
Method variant for Result.unsafelyUnwrapErr

Returns E

unwrapOr

unwrapOr(this: Result<T, E>, defaultValue: T): T

Implementation of ResultShape.unwrapOr
- Defined in result.ts:453
Method variant for Result.unwrapOr

Parameters
- this: Result<T, E>
- defaultValue: T
Returns T

unwrapOrElse

unwrapOrElse(this: Result<T, E>, elseFn: function): T

- Defined in result.ts:458
Method variant for Result.unwrapOrElse

Parameters
- this: Result<T, E>
- elseFn: function
 - - (error: E): T
 - Parameters
 - error: E
 Returns T
Returns T

Static unwrapErr

unwrapErr<F>(theErr: Err<F, any>): F

- Defined in result.ts:325
Unwrap the contained error . A convenience method for functional idioms.

A common scenario where you might want to use this is in a pipeline of functions:
```
import Result, { Ok } from 'true-myth/result';

function getMessages(results: Array<Result<string, Error>>): Array<number> {
return maybeStrings
.filter(Result.isErr)
.map(Err.unwrapErr)
.map(e => e.message);
}
```
Type parameters
- F
Parameters
- theErr: Err<F, any>
Returns F

Type parameters

T

E

Hierarchy

Implements

Index

Constructors

Properties

Methods

Constructors

constructor

Parameters

error: E | null

Returns Err

Properties

error

variant

Methods

and

Type parameters

U

Parameters

this: Result<T, E>

mAnd: Result<U, E>

Returns Result<U, E>

andThen

Type parameters

U

Parameters

this: Result<T, E>

andThenFn: function

Parameters

t: T

Returns Result<U, E>

Returns Result<U, E>

ap

Type parameters

A

B

Parameters

this: Result<function, E>

r: Result<A, E>

Returns Result<B, E>

chain

Type parameters

U

Parameters

this: Result<T, E>

chainFn: function

Parameters

t: T

Returns Result<U, E>

Returns Result<U, E>

equals

Parameters

this: Result<T, E>

comparison: Result<T, E>

Returns boolean

flatMap

Type parameters

U

Parameters

this: Result<T, E>

flatMapFn: function

Parameters

t: T

Returns Result<U, E>

Returns Result<U, E>

isErr

Parameters

this: Result<T, E>

Returns this is Err<T, E>

isOk

Parameters

this: Result<T, E>

Returns this is Ok<T, E>

map

Type parameters

U

Parameters