NGRX4更新

如果您正在迁移到NGRX 4，您可能已经从迁移指南中注意到用于组合reducer的rootreducer方法已经被ActionReducerMap方法所取代。起初，这种新的做事方式可能会使重置状态成为一个挑战。它实际上很简单，但这样做的方式已经改变了。

这个解决方案的灵感来自NGRX4 Github文档的元还原器API部分。

首先，让我们假设你正在使用NGRX的新ActionReducerMap选项像这样组合你的reducer:

//index.reducer.ts
export const reducers: ActionReducerMap<State> = {
    auth: fromAuth.reducer,
    layout: fromLayout.reducer,
    users: fromUsers.reducer,
    networks: fromNetworks.reducer,
    routingDisplay: fromRoutingDisplay.reducer,
    routing: fromRouting.reducer,
    routes: fromRoutes.reducer,
    routesFilter: fromRoutesFilter.reducer,
    params: fromParams.reducer
}

现在，假设你想从app。module内部重置状态

//app.module.ts
import { IndexReducer } from './index.reducer';
import { StoreModule, ActionReducer, MetaReducer } from '@ngrx/store';
...
export function debug(reducer: ActionReducer<any>): ActionReducer<any> {
    return function(state, action) {

      switch (action.type) {
          case fromAuth.LOGOUT:
            console.log("logout action");
            state = undefined;
      }
  
      return reducer(state, action);
    }
  }

  export const metaReducers: MetaReducer<any>[] = [debug];

  @NgModule({
    imports: [
        ...
        StoreModule.forRoot(reducers, { metaReducers}),
        ...
    ]
})

export class AppModule { }

这基本上是用NGRX 4达到同样效果的一种方法。

为了将状态重置为初始状态，我编写了以下代码:

const appReducers = (state, action) =>
   combineReducers({ reducer1, reducer2, user })(
     action.type === "LOGOUT" ? undefined : state,
     action
);

我在使用typescript时的解决方案，建立在Dan Abramov的答案之上(redux类型使得不可能将undefined作为第一个参数传递给reducer，所以我将初始根状态缓存在一个常量中):

// store

export const store: Store<IStoreState> = createStore(
  rootReducer,
  storeEnhacer,
)

export const initialRootState = {
  ...store.getState(),
}

// root reducer

const appReducer = combineReducers<IStoreState>(reducers)

export const rootReducer = (state: IStoreState, action: IAction<any>) => {
  if (action.type === "USER_LOGOUT") {
    return appReducer(initialRootState, action)
  }

  return appReducer(state, action)
}


// auth service

class Auth {
  ...

  logout() {
    store.dispatch({type: "USER_LOGOUT"})
  }
}

这种方法非常正确:销毁任何特定状态“NAME”以忽略并保留其他状态。

const rootReducer = (state, action) => {
    if (action.type === 'USER_LOGOUT') {
        state.NAME = undefined
    }
    return appReducer(state, action)
}

对我来说，最好的工作是设置initialState而不是state:

  const reducer = createReducer(initialState,
  on(proofActions.cleanAdditionalInsuredState, (state, action) => ({
    ...initialState
  })),

下面的解决方案对我很有效。

我添加了重置状态功能到元还原器。关键在于使用

return reducer(undefined, action);

将所有减速器设置为初始状态。返回undefined反而会导致错误，因为存储的结构已经被破坏。

/还原剂index.ts

export function resetState(reducer: ActionReducer<State>): ActionReducer<State> {
  return function (state: State, action: Action): State {

    switch (action.type) {
      case AuthActionTypes.Logout: {
        return reducer(undefined, action);
      }
      default: {
        return reducer(state, action);
      }
    }
  };
}

export const metaReducers: MetaReducer<State>[] = [ resetState ];

app.module.ts

import { StoreModule } from '@ngrx/store';
import { metaReducers, reducers } from './reducers';

@NgModule({
  imports: [
    StoreModule.forRoot(reducers, { metaReducers })
  ]
})
export class AppModule {}