2018-03-14
JiangRen Mr
Redux is a terribly simple library for state management, and has made working with React more manageable for everyone. However, there are a lot of cases where people blindly follow boilerplate code to integrate redux with their React application without understanding all the moving parts involved.
There is an entire library, called react-redux whose sole purpose is to seamlessly integrate redux’s state management into a React application. I feel that it’s important to know what’s going on when you do something that essentially forms the backbone of your application.
At this point it’s hard for some to believe, but redux and React are actually two separate libraries which can and have been used completely independent of each other. Lets take a look at redux’s state management flow :
If you have worked with redux before, you know that its functionality revolves around a “store”, which is where the state of the application lives. There is no way anyone can directly modify the store. The only way to do so is through reducers, and the only way to trigger reducers is to dispatch actions. So ultimately :
To change data, we need to dispatch an action
On the other hand, when we want to retrieve data, we do not get it directly from the store. Instead, we get a snapshot of the data in the store at any point in time using store.getState()
, which gives us the “state” of the application as on the time at which we called the getState
method.
To obtain data we need to get the current state of the store
Now, let’s come to the (simplified) component structure of a standard react todo-mvc application :
If we want to link our React application with the redux store, we first have to let our app know that this store exists. This is where we come to the first major part of the react-redux library, which is the Provider
.
Provider
is a React component given to us by the “react-redux” library. It serves just one purpose : to “provide” the store to its child components.
//This is the store we create with redux's createStore method
const store = createStore(todoApp,{})
// Provider is given the store as a prop
render(
<Provider store={store}>
<App/>
</Provider>, document.getElementById('app-node'))
Since the provider only makes the store accessible to it’s children, and we would ideally want our entire app to access the store, the most sensible thing to do would be to put our App
component within Provider
.
If we were to follow the previous diagram, the Provider
node would be represented as a parent node on top of the App
node. However, because of the utility that Provider
gives us, I feel it’s more appropriate to represent it as something which
Now that we have “provided” the redux store to our application, we can now connect our components to it. We established previously that there is no way to directly interact with the store. We can either retrieve data by obtaining its current state, or change its state by dispatching an action (we only have access to the top and bottom component of the redux flow diagram shown previously).
This is precisely what connect
does. Consider this piece of code, which uses connect
to map the stores state and dispatch to the props of a component :
import {connect} from 'react-redux'
const TodoItem = ({todo, destroyTodo}) => {
return (
<div>
{todo.text}
<span onClick={destroyTodo}> x </span>
</div>
)
}
const mapStateToProps = state => {
return {
todo : state.todos[0]
}
}
const mapDispatchToProps = dispatch => {
return {
destroyTodo : () => dispatch({
type : 'DESTROY_TODO'
})
}
}
export default connect(
mapStateToProps,
mapDispatchToProps
)(TodoItem)
mapStateToProps
and mapDispatchToProps
are both pure functions that are provided the stores “state” and “dispatch” respectively. Furthermore, both functions have to return an object, whose keys will then be passed on as the props of the component they are connected to.
In this case, mapStateToProps
returns an object with only one key : “todo”, and mapDispatchToProps
returns an object with the destroyTodo
key.
The connected component (which is exported) provides todo
and destroyTodo
as props to TodoItem
.
It’s important to note that only components within the Provider
can be connected (In the above diagram, the connect is done through the Provider).
Redux is a powerful tool and even more so when combined with React. It really helps to know why each part of the react-redux
library is used, and hopefully after reading this post, the function of Provider
and connect
is clear.
IT Support 训练营01期
2025/11/10 06:13 (Sydney)
CCNA考证班01期
2025/09/06 08:37 (Sydney)
商业数据分析实战班第17期
2025/03/15 06:13 (Sydney)
地址
Level 10b, 144 Edward Street, Brisbane CBD(Headquarter)Level 2, 171 La Trobe St, Melbourne VIC 3000四川省成都市武侯区桂溪街道天府大道中段500号D5东方希望天祥广场B座45A13号Business Hub, 155 Waymouth St, Adelaide SA 5000Disclaimer
JR Academy acknowledges Traditional Owners of Country throughout Australia and recognises the continuing connection to lands, waters and communities. We pay our respect to Aboriginal and Torres Strait Islander cultures; and to Elders past and present. Aboriginal and Torres Strait Islander peoples should be aware that this website may contain images or names of people who have since passed away.
匠人学院网站上的所有内容,包括课程材料、徽标和匠人学院网站上提供的信息,均受澳大利亚政府知识产权法的保护。严禁未经授权使用、销售、分发、复制或修改。违规行为可能会导致法律诉讼。通过访问我们的网站,您同意尊重我们的知识产权。 JR Academy Pty Ltd 保留所有权利,包括专利、商标和版权。任何侵权行为都将受到法律追究。查看用户协议
© 2017-2024 JR Academy Pty Ltd. All rights reserved.
ABN 26621887572