How to use Generic Type in NgRx createAction props<>()

Question

I want to create an NgRx action creator factory. But I don't know how it is possible to pass in a generic type to the props method.

import { createAction, props } from "@ngrx/store";

function actionFactory<T>(name: string) {
  return createAction(name, props<T>());
//                          ^^^^^^^^^^
}

It throws this error

Type 'Props<T>' provides no match for the signature '(...args: any[]): object'

How do I need to modify the factory method to pass a generic type into the props method like this?:

const action = actionFactory<{ id: string }>("sample");

You can try it yourself on Stackblitz

Answer 1

It seems @ngrx/store - from some reasons - prevents creating actions with empty objects. Here is a possible solution respecting @ngrx/store requirements and making actions fully typed:

import { createAction, props, Props, NotAllowedCheck } from "@ngrx/store";

// T extends object meets the condition of props function
function actionFactory<T extends object>(name: string) {
  // restricting config type to match createAction requirements
  return createAction(name, props<T>() as Props<T> & NotAllowedCheck<T>);
}

// ok
const action = actionFactory<{ id: string }>("sample");

// empty object picked up on type level
const emptyAction = actionFactory<{}>("sample");
emptyAction({}); // error as expected properly

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