ExtractType - API reference

API reference › @evolu/common › Types › ExtractType

type ExtractType<TUnion, TType> = Extract<
  TUnion,
  {
    type: TType;
  }
>;

Defined in: packages/common/src/Types.ts:358

Extracts members of a discriminated union by their type literal.

Constrains TType to valid type values, so typos fail at the type argument instead of silently producing never.

Example

type Message =
  | { readonly type: "Create"; readonly id: string }
  | { readonly type: "Delete"; readonly id: string };

type CreateMessage = ExtractType<Message, "Create">;
// { readonly type: "Create"; readonly id: string }

// Type error: "Cretae" is not a valid Message type
type _Typo = ExtractType<Message, "Cretae">;