---
id: 5a24c314108439a4d4036154
title: Combine Multiple Reducers
challengeType: 6
isRequired: false
videoUrl: ''
localeTitle: 结合多个减速器
---
## Description
当您的应用程序的状态开始变得更加复杂时，可能很容易将状态分成多个部分。相反，请记住Redux的第一个原则：所有应用程序状态都保存在商店中的单个状态对象中。因此，Redux提供减速器组合作为复杂状态模型的解决方案。您可以定义多个reducers来处理应用程序状态的不同部分，然后将这些reducer组合成一个根reducer。然后将根reducer传递给Redux createStore()方法。为了让我们将多个reducer组合在一起，Redux提供了combineReducers()方法。此方法接受一个对象作为参数，您可以在其中定义将键与特定reducer函数关联的属性。 Redux将使用您为密钥指定的名称作为相关状态的名称。通常，当每个应用程序状态以某种方式不同或唯一时，为每个应用程序状态创建一个减速器是一个好习惯。例如，在具有用户身份验证的笔记记录应用程序中，一个reducer可以处理身份验证，而另一个reducer处理用户正在提交的文本和备注。对于这样的应用程序，我们可能会像这样编写combineReducers()方法： const rootReducer = Redux.combineReducers（{
auth：authenticationReducer，
笔记：notesReducer
}）;
现在，关键notes将包含与我们的注释相关联的所有状态，并由notesReducer处理。这就是如何组合多个reducers来管理更复杂的应用程序状态。在此示例中，Redux存储中保存的状态将是包含auth和notes属性的单个对象。
## Instructions
代码编辑器中提供了authReducer() counterReducer()和authReducer()函数以及Redux存储。使用Redux.combineReducers()方法完成rootReducer()函数的Redux.combineReducers() 。指定counterReducer一键叫count和authReducer一个叫关键auth 。
## Tests
```yml
tests:
- text: counterReducer应该递增和递减state 。
testString: 'assert((function() { const initalState = store.getState().count; store.dispatch({type: INCREMENT}); store.dispatch({type: INCREMENT}); const firstState = store.getState().count; store.dispatch({type: DECREMENT}); const secondState = store.getState().count; return firstState === initalState + 2 && secondState === firstState - 1 })(), "The counterReducer should increment and decrement the state.");'
- text: authReducer应切换在true和false之间进行authenticated的state 。
testString: 'assert((function() { store.dispatch({type: LOGIN}); const loggedIn = store.getState().auth.authenticated; store.dispatch({type: LOGOUT}); const loggedOut = store.getState().auth.authenticated; return loggedIn === true && loggedOut === false })(), "The authReducer should toggle the state of authenticated between true and false.");'
- text: 存储state应该有两个键： count ，它包含一个数字， auth ，它包含一个对象。 auth对象应具有authenticated属性，该属性包含布尔值。
testString: 'assert((function() { const state = store.getState(); return typeof state.auth === "object" && typeof state.auth.authenticated === "boolean" && typeof state.count === "number" })(), "The store state should have two keys: count, which holds a number, and auth, which holds an object. The auth object should have a property of authenticated, which holds a boolean.");'
- text: 该rootReducer应该是结合了功能counterReducer和authReducer 。
testString: 'getUserInput => assert((function() { const noWhiteSpace = getUserInput("index").replace(/\s/g,""); return typeof rootReducer === "function" && noWhiteSpace.includes("Redux.combineReducers") })(), "The rootReducer should be a function that combines the counterReducer and the authReducer.");'
```
## Challenge Seed
```jsx
const INCREMENT = 'INCREMENT';
const DECREMENT = 'DECREMENT';
const counterReducer = (state = 0, action) => {
switch(action.type) {
case INCREMENT:
return state + 1;
case DECREMENT:
return state - 1;
default:
return state;
}
};
const LOGIN = 'LOGIN';
const LOGOUT = 'LOGOUT';
const authReducer = (state = {authenticated: false}, action) => {
switch(action.type) {
case LOGIN:
return {
authenticated: true
}
case LOGOUT:
return {
authenticated: false
}
default:
return state;
}
};
const rootReducer = // define the root reducer here
const store = Redux.createStore(rootReducer);
```
## Solution
```js
// solution required
```