错误：预期根化简器是一个函数。相反，收到：'undefined'

Question

我一直遇到这个错误！

错误：根减少器应为函数。相反，收到："未定义">

我已经试过了所有我能找到的答案，但都无济于事，以下是所有相关的东西！

根部还原剂

const createRootReducer = (history) => {
combineReducers({
router: connectRouter(history),
createUser: signupReducer,
});
};
export default createRootReducer;

根

const Root = ({ children, initialState = {} }) => {
const history = createBrowserHistory();
const middleware = [thunk, routerMiddleware(history)];
const store = createStore(rootReducer(history), initialState, applyMiddleware(...middleware));
return (
<Provider store={store}>
<ConnectedRouter history={history}>{ children }</ConnectedRouter>
</Provider>
);
};
export default Root;

应用程序

function App() {
return (
<div className="App">
<Root>
<ToastContainer hideProgressBar={true} newestOnTop={true} />
<Navbar />
<Landing />
<PostList />
</Root>
</div>
);
}
export default App;

和注册减少器

export const signupReducer = (state = initialState, action) => {
switch (action.type) {
case UserTypes.CREATE_USER_SUBMITTED:
return {
usernameError: "",
passwordError: "",
isSubmitted: true
};
case UserTypes.CREATE_USER_SUCCESS:
return {
usernameError: "",
passwordError: "",
isSubmitted: false
};
case UserTypes.CREATE_USER_ERROR:
const err = {
usernameError: "",
passwordError: "",
isSubmitted: false
};
if(action.errorData.hasOwnProperty('username')){
err.usernameError = action.errorData['username'];
}
if(action.errorData.hasOwnProperty('password')){
err.passwordError = action.errorData['password'];
}
return err;
default:
return state
}
}

这是在根组件中抛出错误的行

const store = createStore(rootReducer(history), initialState, applyMiddleware(...middleware));

感谢您抽出时间！

Answer 1

您需要返回组合的减速器。

const createRootReducer = (history) => {
return combineReducers({
router: connectRouter(history),
createUser: signupReducer,
});
};

或者使用箭头函数隐式返回。

const createRootReducer = (history) => combineReducers({
router: connectRouter(history),
createUser: signupReducer,
});

Answer 2

• 当您最初在项目中设置redux，但尚未创建任何reducer时，就会出现此错误
• 所以你必须用假Reducers欺骗Redux
  例如：
  

export default combineReducers({ 
test: () => 'test reducer' 
});

• 在此处创建reducer绑定后
  ，例如：
  

import { combineReducers } from 'redux'; 
import productReducer from './productReducer'
export default combineReducers({ 
products: productReducer 
})