actions-creator.d.ts

/**
 * Type used to declare a type-safe reducer without switch-cases.
 *
 * @example
 * ```ts
 * interface State {
 *   loading: boolean;
 * }
 *
 * type Action = Readonly<
 *   | { type: 'setLoading'; payload: boolean }
 *   | { type: 'doSomething'; payload: any }
 * >;
 *
 * export const actions: ActionsCreator<Action, State> = (state) => ({
 *   // the `payload` argument already has the correct type (`boolean`)
 *   // and the method is already expected to return a `State`.
 *   setLoading(payload) {
 *     return {
 *       ...state,
 *       loading,
 *     }
 *   },
 *
 *   // will throw a compilation error if all actions are not implemented
 *   // like in this example, `doSomething` is missing
 * });
 *
 * export const reducer = (state: Model, { type, payload }: Action): Model => {
 *   // @ts-ignore
 *   return actions(state)[type]?.(payload) || state;
 * };
 * ```
 */
export type ActionsCreator<T extends { type: string; payload?: any }, S = any> = (
  state: S,
) => {
  [K in T['type']]: (action: Extract<T, { type: K }>['payload']) => S;
};