Variable: fromPromise()

readonly fromPromise: {<T>(executor): AsyncResult<T, Error>; <T, E>(executor, onError): AsyncResult<T, E>; }

Defined in: core/factories.ts:196

Call Signature

<T>(executor): AsyncResult<T, Error>

Wraps async function execution in Result, capturing rejections.

Converts Promises that may reject into Results, allowing explicit handling without try/catch or .catch().

Type Parameters

T

T

Resolved value type

Parameters

executor

() => Promise<T>

Async function to execute

Returns

AsyncResult<T, Error>

Promise of Ok with value or Err if rejects

Examples

// Fetch API
const response = await Result.fromPromise(
  async () => {
    const res = await fetch('/api/user')
    return res.json()
  }
)

if (response.isOk()) {
  console.log(response.unwrap())
}

// Chained async operations
const user = await Result.fromPromise(async () => {
  const data = await db.query('SELECT * FROM users WHERE id = ?', [id])
  if (!data[0]) throw new Error('User not found')
  return data[0]
})

// Async file I/O
const content = await Result.fromPromise(
  () => fs.promises.readFile('file.txt', 'utf-8')
)

Call Signature

<T, E>(executor, onError): AsyncResult<T, E>

Wraps Promise in Result with custom error transformation.

Type Parameters

T

T

Resolved value type

E

E

Error type

Parameters

executor

() => Promise<T>

Async function to execute

onError

(error) => E

Function that transforms the rejection error

Returns

AsyncResult<T, E>

Promise of Ok or Err with custom error

Examples

// Typed error
type NetworkError = { type: 'network'; status?: number }
const data = await Result.fromPromise(
  () => fetch('/api/data').then(r => r.json()),
  (err): NetworkError => ({
    type: 'network',
    status: err instanceof Response ? err.status : undefined
  })
)

// Contextualizing errors
const user = await Result.fromPromise(
  () => fetchUser(id),
  (err) => new Error(`Failed to fetch user ${id}: ${err}`)
)