为什么 combineReducers 不在 Redux 中接收状态？

Question

当我查看通过 combineReducers 调用的 reducer 时，它没有获取参数中的状态或操作。

我的减速器文件是这样的：

import { combineReducers } from 'redux';
import nav from './reducers/nav';
import pages from './reducers/pages';
import entities from './reducers/entities';

export default function(initialData) {

  return function(state, action) {
    if (!state) {
      console.log('no state', initialData);
      return initialData;
    }

    // This is showing state as having expected value
    console.log('state', state);

    return combineReducers({
      nav,
      pages,
      entities
    });
  }
};

我的店铺初始化是这样的：

import reducerWrapper from './reducers';

// Initial state is defined above
var reducers = reducerWrapper(initialState),
    store = Redux.createStore(reducers, initialState);

example code on the site 不使用包装器（我在其他示例中看到过）。我也试过了，但没有用。我的意思是在这两个例子中，我不确定它是如何得到 state/action 给定的。我觉得我在这里缺少一些魔法。

已更新 现在是减速器文件：

import { combineReducers } from 'redux';
import nav from './reducers/nav';
import pages from './reducers/pages';
import entities from './reducers/entities';

export default combineReducers({
  nav,
  pages,
  entities
});

后跟 store = Redux.createStore(reducerWrapper, initialState)，也不起作用，即使我删除了 reducerWrapper 内的包装并仅导出默认的 combineReducers`

Answer 1

combineReducers returns 需要用state和action调用的函数。您可以直接导出：

const rootReducer = combineReducers(...);
export default rootReducer;

或者你可以像现在这样包装它：

const rootReducer = combineReducers(...);
export default function (initialData) {
  return function (state, action) {
    if (!state) {
      console.log('no state', initialData);
      return initialData;
    }

    // This is showing state as having expected value
    console.log('state', state);

    return rootReducer(state, action);
  }
}

Answer 2

这里不容易看到答案。问题是我的减速器没有默认状态。

商店在此处触发 INIT 事件：https://github.com/reactjs/redux/blob/master/src/createStore.js#L204

然后它最终到达这里： https://github.com/reactjs/redux/blob/master/src/combineReducers.js#L52

意思是如果我的reducer是function (state, action) { return state }而不是function (state='anyDefaultValue') { return state }，combineReducer会报错说reducer没有return状态

为什么 combineReducers 不在 Redux 中接收状态？

Why isn't combineReducers receiving state in Redux?

reactjs

react-redux