RequireExactlyOne

Since 1.3.0

Require exactly one of the specified keys to be present in an object type.

Signature

type RequireExactlyOne<T, K extends keyof T = keyof T> = K extends K
  ? Omit<T, K> & Required<Pick<T, K>> & Partial<Omit<T, K>>
  : never

Parameters

Parameter	Description
T	The object type
K	The keys where exactly one must be present (defaults to all keys)

Examples

Basic Usage

import type { RequireExactlyOne } from 'uni-types'

type Identifier = { id?: number; uuid?: string; slug?: string }
type SingleIdentifier = RequireExactlyOne<Identifier, 'id' | 'uuid' | 'slug'>
// Must have exactly one of id, uuid, or slug

For Mutually Exclusive Options

type Config = { url?: string; file?: string; data?: object }
type SourceConfig = RequireExactlyOne<Config, 'url' | 'file' | 'data'>
// Must provide exactly one source

With Default Behavior

type Options = { a?: number; b?: string }
type ExactlyOne = RequireExactlyOne<Options>
// Must have exactly one of a or b (not both)

Related

• RequireAtLeastOne - Require at least one key
• RequireKeys - Make specific keys required