如何处理使用ngrx时遇到的错误消息: NullInjectorError R3InjectorError(AppModule)[StoreFeatureModule]

错误消息：

main.ts:12 NullInjectorError: R3InjectorError(AppModule)[StoreFeatureModule -> ReducerManager -> ReducerManager -> ReducerManager]:

NullInjectorError: No provider for ReducerManager!

at NullInjector.get (http://localhost:4200/vendor.js:8310:27)

at R3Injector.get (http://localhost:4200/vendor.js:22317:33)

at injectInjectorOnly (http://localhost:4200/vendor.js:8165:33)

at Module.ɵɵinject (http://localhost:4200/vendor.js:8175:57)

at Object.StoreFeatureModule_Factory [as factory] (http://localhost:4200/vendor.js:64143:380)

at R3Injector.hydrate (http://localhost:4200/vendor.js:22555:63)

at R3Injector.get (http://localhost:4200/vendor.js:22305:33)

at http://localhost:4200/vendor.js:22351:25

根据这篇文章的提示：

https://www.manongdao.com/article-974354.html

StoreModule.forRoot should only be called once in the root of your project NgModule. If you wan’t to register a feature, use StoreModule.forFeature. Using forRoot registers the global providers needed for Store.

在app module里添加一行代码即可解决：