ngrx - 如何在 getReducers() : ActionReducerMap 中返回 reducer 映射？

Question

我正在尝试注入(inject) 特征 reducer 通过 NgRx 功能模块组成状态时。

import { NgModule, InjectionToken } from '@angular/core';
import { StoreModule, ActionReducerMap } from '@ngrx/store';

import * as fromFeature from './reducers';

export const FEATURE_REDUCER_TOKEN = new InjectionToken<ActionReducerMap<fromFeature.State>>('Feature Reducers');

我应该在这里返回什么？

export function getReducers(): ActionReducerMap<fromFeature.State> {
  // map of reducers
  return {
  
  };
}

我试过

export function getReducers(): ActionReducerMap<fromFeature.State> {
      // map of reducers
      return {
          reducerA: FeatureAReducer
      };
    }

但它给出了错误对象文字可能只指定已知属性。
其余模块代码:

@NgModule({
  imports: [
    StoreModule.forFeature('feature', FEATURE_REDUCER_TOKEN),
  ],
  providers: [
    {
      provide: FEATURE_REDUCER_TOKEN,
      useFactory: getReducers
    }
  ]
})
export class FeatureModule { }

Answer 1

我认为每个 reducer，无论是 root 还是 feature reducer，都会返回一个新的 state 对象。但实际上并没有。什么功能减少器，它只返回它更新的状态段。
来自 ngrx/platform/example-app :

we treat each reducer like a table in a database. This means ourtop level state interface is just a map of keys to inner state types.