ml-1.ts

export interface DemoState {
  someProp: number;
}

export function createInitialState(): DemoState {
  return {
    someProp: 0
  };
}

@StoreConfig({ name: 'demo' })
export class DemoStore extends Store<DemoState> {
  constructor() {
    super(createInitialState());
  }
}

ml-2.ts

export class DemoQuery extends Query<DemoState> {
  selectSomeProp$ = this.select(state => state.someProp);

  constructor(protected store: DemoStore) {
    super(store);
  }
}