Unions

GraphQL unions can be defined by placing a @gqlUnion docblock directly before a:

• Type alias of a union of object types

/**
 * A description of my union.
 * @gqlUnion <optional name of the union, if different from type name>
 */
type MyUnion = User | Post;

/** @gqlType */
class User {
  __typename: "User";
  /** @gqlField */
  name: string;
}

/** @gqlType */
class Post {
  __typename: "Post";
  /** @gqlField */
  content: string;

  /** @gqlField */
  author: User;
}

note

All the types referenced in the TypeScript union but be explicitly annotated with @gqlType. Grats will remind you with a helpful error message if you forget.

note

Grats must be able to determine the typename of any type which members of a union. To achieve this Grats will validate that all member types either define a __typename: "MyType" as const property or are exported classes. Grats can use either to determin the typename at runtime.