Class: Err<E>
A type used to express computations that can fail, it can be used for returning and propagating errors. This is a
type union with the variants Ok(T)
, representing success and containing a value, and Err(E)
, representing error
and containing an error value.
Typeparam
T The result's type.
Typeparam
E The error's type.
See
https://doc.rust-lang.org/std/result/index.html
Type Parameters
Type Parameter |
---|
E |
Implements
IResult
<any
,E
>
Constructors
new Err()
new Err<
E
>(error
:E
):Err
<E
>
Parameters
Parameter | Type |
---|---|
error | E |
Returns
Err
<E
>
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:12
Methods
[iterator]()
[iterator]():
Generator
<never
,any
,unknown
>
Returns an iterator over the possibly contained value.
The iterator yields one value if the result is Ok
, otherwise none.
Returns
Generator
<never
, any
, unknown
>
Examples
const x = ok(7);
for (const value of x) {
console.log(value);
}
// Logs 7
const x = err('Nothing!');
for (const value of x) {
console.log(value);
}
// Doesn't log
See
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:182
and()
and(
result
?:Result
<any
,E
>):this
Returns result
if the result is Ok
, otherwise returns the Err
value of itself.
Parameters
Parameter | Type | Description |
---|---|---|
result ? | Result <any , E > | The result to check. |
Returns
this
Examples
const x: Result<number, string> = ok(2);
const y: Result<string, string> = err('Late error');
assert.equal(x.and(y), err('Late error'));
const x: Result<number, string> = err('Early error');
const y: Result<string, string> = err('Late error');
assert.equal(x.and(y), err('Early error'));
const x: Result<number, string> = ok(2);
const y: Result<string, string> = ok('Hello');
assert.equal(x.and(y), ok('Hello'));
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.and
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:123
andThen()
andThen(
cb
?: (value
:never
) =>Result
<any
,E
>):this
Calls cb
if the result is Ok
, otherwise returns the Err
value of self.
This function can be used for control flow based on Result
values.
Parameters
Parameter | Type | Description |
---|---|---|
cb ? | (value : never ) => Result <any , E > | The predicate. |
Returns
this
Example
function fractionOf4(value: number) {
return value === 0 ? err('overflowed') : ok(4 / value);
}
assert.equal(ok(2).andThen(fractionOf4), ok(4));
assert.equal(ok(0).andThen(fractionOf4), err('overflowed'));
assert.equal(err('not a number').andThen(fractionOf4), err('not a number'));
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.and_then
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:128
contains()
contains(
value
?:any
):false
Returns true
if the result is an Ok
and the given value strict equals it.
Parameters
Parameter | Type | Description |
---|---|---|
value ? | any | The value to compare. |
Returns
false
Examples
const x: Result<number, string> = ok(2);
assert.equal(x.contains(2), true);
const x: Result<number, string> = ok(3);
assert.equal(x.contains(2), false);
const x: Result<number, string> = err('Some error message');
assert.equal(x.contains(2), false);
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.contains
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:141
containsErr()
containsErr(
error
:E
):boolean
Returns true
if the result is an Err
and the given error strict equals it.
Parameters
Parameter | Type | Description |
---|---|---|
error | E | The error to compare. |
Returns
boolean
Examples
const x: Result<number, string> = ok(2);
assert.equal(x.containsErr('Some error message'), false);
const x: Result<number, string> = err('Some error message');
assert.equal(x.containsErr('Some error message'), true);
const x: Result<number, string> = err('Some other error message');
assert.equal(x.containsErr('Some error message'), false);
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.contains_err
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:146
eq()
eq(other)
eq(
other
:Ok
<any
>):false
Checks whether or not other
equals with self.
Parameters
Parameter | Type | Description |
---|---|---|
other | Ok <any > | The other result to compare. |
Returns
false
See
https://doc.rust-lang.org/std/cmp/trait.PartialEq.html#tymethod.eq
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:166
eq(other)
eq(
other
:Result
<any
,E
>):boolean
Checks whether or not other
equals with self.
Parameters
Parameter | Type | Description |
---|---|---|
other | Result <any , E > | The other result to compare. |
Returns
boolean
See
https://doc.rust-lang.org/std/cmp/trait.PartialEq.html#tymethod.eq
Implementation of
IResult.eq
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:167
err()
err():
Some
<E
>
Converts from Result<T, E>
to Option<E>
.
Converts itself into an Option<E>
, and discarding the successful value, if any.
Returns
Some
<E
>
Examples
const x: Result<number, string> = ok(2);
assert.equal(x.err(), none);
const x: Result<number, string> = err('Some error message');
assert.equal(x.err(), 'Some error message');
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.err
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:37
expect()
expect(
message
:string
):never
Returns the contained Ok
value.
If the value is an Err
, it throws a ResultError with the given message and the content of the Err
.
Parameters
Parameter | Type | Description |
---|---|---|
message | string | The message for the error. |
Returns
never
Examples
const x = ok(2);
assert.equal(x.expect('Whoops!'), 2);
const x = err('Emergency failure');
assert.throws(() => x.expect('Whoops!'), {
name: 'ResultError',
message: 'Whoops',
value: 'Emergency failure'
});
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.expect
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:93
expectErr()
expectErr(
message
?:string
):E
Returns the contained Err
value.
If the value is an Ok
, it throws a ResultError with the given message and the content of the Ok
.
Parameters
Parameter | Type | Description |
---|---|---|
message ? | string | The message for the error. |
Returns
E
Examples
const x = ok(2);
assert.throws(() => x.expectErr('Whoops!'), {
name: 'ResultError',
message: 'Whoops',
value: 2
});
const x = err('Emergency failure');
assert.equal(x.expectErr('Whoops!'), 'Emergency failure');
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.expect_err
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:97
flatten()
flatten():
this
Converts from Result<Result<T, E>, E>
to Result<T, E>
.
Returns
this
Examples
const x: Result<Result<string, number>, number> = ok(ok('Hello'));
assert.equal(x.flatten(), ok('Hello'));
const x: Result<Result<string, number>, number> = ok(err(6));
assert.equal(x.flatten(), err(6));
const x: Result<Result<string, number>, number> = err(6);
assert.equal(x.flatten(), err(6));
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.flatten
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:154
inspect()
inspect(
cb
?: (value
:never
) =>void
):this
Calls the provided closure with a reference to the contained value (if Ok
).
Parameters
Parameter | Type | Description |
---|---|---|
cb ? | (value : never ) => void | The predicate. |
Returns
this
Seealso
inspectAsync for the awaitable version.
Examples
ok(2).inspect(console.log);
// Logs: 2
err('Some error message').inspect(console.log);
// Doesn't log
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.inspect
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:69
inspectAsync()
inspectAsync(
cb
?: (value
:never
) =>unknown
):Promise
<Err
<E
>>
Calls the provided closure with a reference to the contained value (if Ok
) and awaits it.
Parameters
Parameter | Type | Description |
---|---|---|
cb ? | (value : never ) => unknown | The predicate. |
Returns
Seealso
inspect for the sync version.
Examples
await ok(2).inspectAsync(console.log);
// Logs: 2
await err('Some error message').inspectAsync(console.log);
// Doesn't log
Note
This is an extension not supported in Rust
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:74
inspectErr()
inspectErr(
cb
: (error
:E
) =>void
):this
Calls the provided closure with a reference to the contained error (if Err
).
Parameters
Parameter | Type | Description |
---|---|---|
cb | (error : E ) => void | The predicate. |
Returns
this
Seealso
inspectErrAsync for the awaitable version.
Examples
ok(2).inspectErr(console.log);
// Doesn't log
err('Some error message').inspectErr(console.log);
// Logs: Some error message
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.inspect_err
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:79
inspectErrAsync()
Calls the provided closure with a reference to the contained error (if Err
) and awaits it.
Parameters
Parameter | Type | Description |
---|---|---|
cb | (error : E ) => unknown | The predicate. |
Returns
Seealso
inspectErr for the sync version.
Examples
await ok(2).inspectErrAsync(console.log);
// Doesn't log
await err('Some error message').inspectErrAsync(console.log);
// Logs: Some error message
Note
This is an extension not supported in Rust
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:84
intoOkOrErr()
intoOkOrErr():
E
Returns the Ok
value if self is Ok
, and the Err
value if self is Err
.
Returns
E
Examples
let x: Result<number, number> = ok(3);
assert.equal(x.intoOkOrErr(), 3);
let x: Result<number, number> = err(4);
assert.equal(x.intoOkOrErr(), 4);
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.into_ok_or_err
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:158
intoPromise()
Returns a Promise
object with the awaited value (if Ok
) or the awaited error (if Err
).
Returns
Example
let x = ok(Promise.resolve(3));
assert.equal(await x.intoPromise(), ok(3));
Note
This is an extension not supported in Rust
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:162
isErr()
isErr():
this is Err<E>
Returns true
if the result is Err
.
Returns
this is Err<E>
Examples
const x = ok(-3);
assert.equal(x.isErr(), false);
const x = err('Some error message');
assert.equal(x.isErr(), true);
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.is_err
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:25
isErrAnd()
isErrAnd(
cb
: (error
:E
) =>boolean
):boolean
Returns true
if the result is Err
and the value inside of it matches a predicate.
Parameters
Parameter | Type | Description |
---|---|---|
cb | (error : E ) => boolean | The predicate. |
Returns
boolean
Examples
const x = ok(2);
assert.equal(x.isErrAnd((error) => error instanceof TypeError), false);
const x = err(new Error('Some error message'));
assert.equal(x.isErrAnd((error) => error instanceof TypeError), false);
const x = err(new TypeError('Some error message'));
assert.equal(x.isErrAnd((error) => error instanceof TypeError), true);
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.is_err_and
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:29
isOk()
isOk():
false
Returns true
if the result is Ok
.
Returns
false
Examples
const x = ok(-3);
assert.equal(x.isOk(), true);
const x = err('Some error message');
assert.equal(x.isOk(), false);
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.is_ok
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:16
isOkAnd()
isOkAnd(
cb
?: (value
:never
) =>boolean
):false
Returns true
if the result is Ok
and the value inside of it matches a predicate.
Parameters
Parameter | Type |
---|---|
cb ? | (value : never ) => boolean |
Returns
false
Examples
const x = ok(2);
assert.equal(x.isOkAnd((value) => value > 1), true);
const x = ok(0);
assert.equal(x.isOkAnd((value) => value > 1), false);
const x = err('Some error message');
assert.equal(x.isOkAnd((value) => value > 1), false);
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.is_ok_and
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:20
iter()
iter():
Generator
<never
,any
,unknown
>
Returns an iterator over the possibly contained value.
The iterator yields one value if the result is Ok
, otherwise none.
Returns
Generator
<never
, any
, unknown
>
Examples
const x = ok(7);
for (const value of x.iter()) {
console.log(value);
}
// Logs 7
const x = err('Nothing!');
for (const value of x.iter()) {
console.log(value);
}
// Doesn't log
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.iter
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:89
map()
map(
cb
?: (value
:never
) =>unknown
):this
Maps a Result<T, E>
to Result<U, E>
by applying a function to a contained Ok
value, leaving an Err
value
untouched.
Parameters
Parameter | Type | Description |
---|---|---|
cb ? | (value : never ) => unknown | The predicate. |
Returns
this
Examples
const x: Result<number, string> = ok(2);
assert.equal(x.map((value) => value * 2), ok(4));
const x: Result<number, string> = err('Some error message');
assert.equal(x.map((value) => value * 2), err('Some error message'));
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.map
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:41
mapErr()
mapErr<
F
>(cb
: (error
:E
) =>F
):Err
<F
>
Maps a Result<T, E>
to Result<T, F>
by applying a function to a contained Err
value, leaving an Ok
value
untouched.
This function can be used to pass through a successful result while handling an error.
Type Parameters
Type Parameter |
---|
F |
Parameters
Parameter | Type | Description |
---|---|---|
cb | (error : E ) => F | The predicate. |
Returns
Err
<F
>
Examples
const x: Result<number, Error> = ok(2);
assert.equal(x.mapErr((error) => error.message), ok(2));
const x: Result<number, Error> = err(new Error('Some error message'));
assert.equal(x.mapErr((error) => error.message), err('Some error message'));
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.map_err
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:61
mapErrInto()
mapErrInto<
R
>(cb
: (error
:E
) =>R
):R
Maps a Result<T, E>
to Result<T, F>
by applying a function to a contained Err
value, leaving an Ok
value
untouched.
This function can be used to pass through a successful result while handling an error.
Unlike mapErr, this method does not wrap the returned value inside Err
, but instead, it returns the
returned value.
Type Parameters
Type Parameter |
---|
R extends Result <any , any > |
Parameters
Parameter | Type | Description |
---|---|---|
cb | (error : E ) => R | The predicate. |
Returns
R
Examples
const x: Result<number, Error> = ok(2);
assert.equal(x.mapErrInto((error) => err(error.message)), ok(2));
const x: Result<number, Error> = err(new Error('Some error message'));
assert.equal(x.mapErrInto((error) => err(error.message)), err('Some error message'));
const x: Result<number, Error> = err(new Error('Some error message'));
assert.equal(x.mapErrInto((error) => ok(4)), ok(4));
Note
This is an extension not supported in Rust
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:65
mapInto()
mapInto(
cb
: (value
:never
) =>Result
<any
,any
>):this
Maps a Result<T, E>
to Result<T, F>
by applying a function to a contained Ok
value, leaving an Err
value
untouched.
Unlike map, this method does not wrap the returned value inside Ok
, but instead, it returns the
returned value.
Parameters
Parameter | Type | Description |
---|---|---|
cb | (value : never ) => Result <any , any > | The predicate. |
Returns
this
Examples
const x: Result<number, string> = ok(2);
assert.equal(x.mapInto((value) => ok(value * value)), ok(4));
const x: Result<number, string> = ok(0);
assert.equal(
x.mapInto((value) => (value === 0 ? err('zero is not divisible') : ok(1 / value))),
err('zero is not divisible')
);
const x: Result<number, string> = err('Some error message');
assert.equal(x.mapInto((value) => ok(4)), err('Some error message'));
Note
This is an extension not supported in Rust
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:46
mapOr()
mapOr<
U
>(defaultValue
:U
,cb
?: (value
:never
) =>U
):U
Returns the provided default (if Err
), or applies a function to the contained value (if Ok
),
Arguments passed to mapOr
are eagerly evaluated; if you are passing the result of a function call, it is
recommended to use mapOrElse
, which is lazily evaluated.
Type Parameters
Type Parameter |
---|
U |
Parameters
Parameter | Type | Description |
---|---|---|
defaultValue | U | The default value to use. |
cb ? | (value : never ) => U | The predicate. |
Returns
U
Examples
const x = ok('hello');
assert.equal(x.mapOr(42, (value) => value.length), 5);
const x = err('Some error message');
assert.equal(x.mapOr(42, (value) => value.length), 42);
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.map_or
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:51
mapOrElse()
mapOrElse<
U
>(op
: (error
:E
) =>U
,cb
?: (value
:never
) =>U
):U
Maps a Result<T, E>
to U
by applying fallback function default to a contained Err
value, or function cb
to a contained Ok
value.
This function can be used to unpack a successful result while handling an error.
Type Parameters
Type Parameter |
---|
U |
Parameters
Parameter | Type | Description |
---|---|---|
op | (error : E ) => U | The predicate that is run on Err . |
cb ? | (value : never ) => U | The predicate that is run on Ok . |
Returns
U
Examples
const x: Result<string, string> = ok('hello');
assert.equal(x.mapOrElse((error) => error.length, (value) => value.length), 5);
const x: Result<string, string> = err('Some error message');
assert.equal(x.mapOrElse((error) => error.length, (value) => value.length), 18);
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.map_or_else
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:56
match()
match<
OkValue
,ErrValue
>(branches
:object
):ErrValue
Runs ok
function if self is Ok
, otherwise runs err
function.
Type Parameters
Type Parameter |
---|
OkValue |
ErrValue |
Parameters
Parameter | Type | Description |
---|---|---|
branches | object | The branches to match. |
branches.err | - | |
branches.ok | - |
Returns
ErrValue
Examples
const result = ok(4).match({
ok: (v) => v,
err: () => 0
});
assert.equal(result, 4);
const result = err('Hello').match({
ok: (v) => v,
err: () => 0
});
assert.equal(result, 0);
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:178
ne()
ne(other)
ne(
other
:Ok
<any
>):true
Checks whether or not other
doesn't equal with self.
Parameters
Parameter | Type | Description |
---|---|---|
other | Ok <any > | The other result to compare. |
Returns
true
See
https://doc.rust-lang.org/std/cmp/trait.PartialEq.html#method.ne
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:172
ne(other)
ne(
other
:Result
<any
,E
>):boolean
Checks whether or not other
doesn't equal with self.
Parameters
Parameter | Type | Description |
---|---|---|
other | Result <any , E > | The other result to compare. |
Returns
boolean
See
https://doc.rust-lang.org/std/cmp/trait.PartialEq.html#method.ne
Implementation of
IResult.ne
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:173
ok()
ok():
None
Converts from Result<T, E>
to Option<T>
.
Converts itself into an Option<T>
, and discarding the error, if any.
Returns
Examples
const x: Result<number, string> = ok(2);
assert.equal(x.ok(), some(2));
const x: Result<number, string> = err('Some error message');
assert.equal(x.ok(), none);
See
https://doc.rust-lang.org/std/result/enum.Result.html#method.ok
Implementation of
Defined in
projects/utilities/packages/result/src/lib/Result/Err.ts:33
or()
or<
R
>(result
:R
):R
Return result
if the result is Err
, otherwise returns the Ok
value of self.
Arguments passed to or are eagerly evaluated; if you are passing the result of a function call, it is recommended to use orElse, which is lazily evaluated.
Type Parameters
Type Parameter |
---|
R extends Result <any , any > |