Using NGRX library for redux, trying to group the state of the application as below

export interface ApplicationState {
    adminState: AdminState
}

export interface AdminState {
    adminProductCategory: ProductCategoryState;
    adminProductVendor: VendorState;
    adminProductSubCategory: ProductSubCategoryState;
    products: ProductsState;
    product: ProductState
}

For the app module

imports: [
    StoreModule.forRoot(reducers, { metaReducers }),
    EffectsModule.forRoot([]),
    StoreDevtoolsModule.instrument({
      maxAge: 25
    })
  ],

Index.ts

export const reducers: ActionReducerMap<ApplicationState> = {
  adminState: AdminState = {
    adminProductCategory: AdminProductCategoryReducer,
    adminProductVendor: AdminProductVendorReducer,
    adminProductSubCategory: AdminProductSubCategoryReducer,
    products: ProductsReducer,
    product: ProductReducer,
  }
};


export const metaReducers: MetaReducer<ApplicationState>[] = [];

Exception

Type '{ adminProductCategory: (state: ProductCategoryState, action: Action) => any; adminProductVendor: (state: VendorState, action: Action) => any; adminProductSubCategory: (state: ProductSubCategoryState, action: Action) => any; products: (state: ProductsState, action: Action) => any; product: (state: ProductState, acti...' is not assignable to type 'ActionReducer<AdminState, Action>'.

'AdminState' only refers to a type, but is being used as a value here.

Reducer

export function AdminProductCategoryReducer(state: ProductCategoryState | undefined, action: Action): any {
  return reducer(state, action);
}