index.ts

import {createSelector, createFeatureSelector, Action, combineReducers} 
    from '@ngrx/store';
import * as fromRoot from '../../../core/store/reducers';
import * as fromIpfs from './ipfs-product-image.reducer';
import * as fromProducts from './purchase-contract.reducer';

export interface PurchaseContractState {
    ipfs: fromIpfs.State;
    products: fromProducts.State;
  }

export interface AppState extends fromRoot.AppState {
    purchaseContract: PurchaseContractState;
  }

export function reducers(state: PurchaseContractState | undefined, action: Action) {
    return combineReducers({
      ipfs: fromIpfs.reducer,
      products: fromProducts.reducer
    })(state, action);
  }