Variable: fromNullable()

readonly fromNullable: {<T>(value): Result<NonNullable<T>, Error>; <T, E>(value, onError): Result<NonNullable<T>, E>; }

Defined in: core/factories.ts:274

Call Signature

<T>(value): Result<NonNullable<T>, Error>

Creates a Result from a value that may be null or undefined.

Useful for working with APIs that return nullable values and you want to force explicit handling of the null/undefined case.

Type Parameters

T

T

Value type

Parameters

value

Possibly null/undefined value

T | null | undefined

Returns

Result<NonNullable<T>, Error>

Ok if defined, Err with default error if null/undefined

Examples

// With present value
const value = Result.fromNullable(42)
// Ok(42)

// With null
const empty = Result.fromNullable(null)
// Err(Error: Value is null or undefined)

// Practical usage with find
const users = [{ id: 1, name: 'Ana' }, { id: 2, name: 'Bob' }]
const user = Result.fromNullable(
  users.find((u) => u.id === 3)
)
// Err(Error: Value is null or undefined)

Call Signature

<T, E>(value, onError): Result<NonNullable<T>, E>

Creates a Result from nullable value with custom error.

Type Parameters

T

T

Value type

E

E

Error type

Parameters

value

Possibly null/undefined value

T | null | undefined

onError

() => E

Function that generates custom error

Returns

Result<NonNullable<T>, E>

Ok if defined, Err with custom error if null/undefined

Examples

// With personalized error
const config = Result.fromNullable(
  process.env.API_KEY,
  () => new Error('API_KEY not configured')
)

// With custom error type
type NotFoundError = { code: 'NOT_FOUND'; resource: string }
const user = Result.fromNullable(
  userMap.get(userId),
  (): NotFoundError => ({ code: 'NOT_FOUND', resource: 'user' })
)