和StoreFeatureModule相关的一个错误消息：

main.ts:12 NullInjectorError: R3InjectorError(AppModule)[StoreFeatureModule -> ReducerManager -> ReducerManager -> ReducerManager]: NullInjectorError: No provider for ReducerManager! at NullInjector.get (http://localhost:4200/vendor.js:62758:27) at R3Injector.get (http://localhost:4200/vendor.js:76765:33) at R3Injector.get (http://localhost:4200/vendor.js:76765:33) at R3Injector.get (http://localhost:4200/vendor.js:76765:33) at injectInjectorOnly (http://localhost:4200/vendor.js:62613:33) at Module.ɵɵinject (http://localhost:4200/vendor.js:62623:57) at Object.StoreFeatureModule_Factory [as factory] (http://localhost:4200/vendor.js:139469:380) at R3Injector.hydrate (http://localhost:4200/vendor.js:77003:63) at R3Injector.get (http://localhost:4200/vendor.js:76753:33) at http://localhost:4200/vendor.js:76799:25

实例化StoreFeatureModule token：

使用factory构建token value：

取reducerManager：

报错：

恢复这行被注释掉的代码之后：

看看StoreModule.forRoot的实现源代码：

class StoreModule {
    /**
     * @param {?} reducers
     * @param {?=} config
     * @return {?}
     */
    static forRoot(reducers, config = {}) {
        return {
            ngModule: StoreRootModule,
            providers: [
                {
                    provide: _ROOT_STORE_GUARD,
                    useFactory: _provideForRootGuard,
                    deps: [[Store, new Optional(), new SkipSelf()]],
                },
                { provide: _INITIAL_STATE, useValue: config.initialState },
                {
                    provide: INITIAL_STATE,
                    useFactory: _initialStateFactory,
                    deps: [_INITIAL_STATE],
                },
                { provide: _INITIAL_REDUCERS, useValue: reducers },
                {
                    provide: _STORE_REDUCERS,
                    useExisting: reducers instanceof InjectionToken ? reducers : _INITIAL_REDUCERS,
                },
                {
                    provide: INITIAL_REDUCERS,
                    deps: [Injector, _INITIAL_REDUCERS, [new Inject(_STORE_REDUCERS)]],
                    useFactory: _createStoreReducers,
                },
                {
                    provide: USER_PROVIDED_META_REDUCERS,
                    useValue: config.metaReducers ? config.metaReducers : [],
                },
                {
                    provide: _RESOLVED_META_REDUCERS,
                    deps: [META_REDUCERS, USER_PROVIDED_META_REDUCERS],
                    useFactory: _concatMetaReducers,
                },
                {
                    provide: _REDUCER_FACTORY,
                    useValue: config.reducerFactory
                        ? config.reducerFactory
                        : combineReducers,
                },
                {
                    provide: REDUCER_FACTORY,
                    deps: [_REDUCER_FACTORY, _RESOLVED_META_REDUCERS],
                    useFactory: createReducerFactory,
                },
                ACTIONS_SUBJECT_PROVIDERS,
                REDUCER_MANAGER_PROVIDERS,
                SCANNED_ACTIONS_SUBJECT_PROVIDERS,
                STATE_PROVIDERS,
                STORE_PROVIDERS,
                provideRuntimeChecks(config.runtimeChecks),
            ],
        };
    }

这里就提供了之前报错信息里缺失的reducer：