By generic I mean a fetch() call is not tied to a single component.
Where should I put this fetch() call? Currently I have it in the top level React component. I simply return null and it does not render anything but it does run and populate redux.
This method seems a bit hacky and was wondering if React provides a way, or is there a common design pattern, to say fetch data that is not tied to a single component.
In general how should I do this?
I would like to write a simple JavaScript function, and then disptach() the data to redux, but React will not let me use dispatch inside a non-rendered JS function.
In general how does one write fetch() when the fetch() is not tied to a single component, and also when this fetch() needs to use dispatch().
// hacky way
import React from 'react';
import { useDispatch } from 'react-redux';
export default () => {
const dispatch = useDispatch();
// run fetch() here
return null;
};
I just started learning react hooks and react-redux hooks and as far I understood everything. But one thing is keep drilling my brain, so I would like to ask more experienced developers here.
If I have more robust app, where I intend to have Redux taking care of whole state and wanna use React hooks fro side effects, do I really need React Hooks?
I have separate functional layer (containers => where all the decisions are being made with redux) and displaying layer (components => where components are dumb and obtain just data they are suppose to render)
Whats bugging me is I make a API call in initial page loading and I would like to use useEffect hook, but im not conviced I should do that when I can useSelector from redux and useDispatch.
here is the code I would like to update into hook style:
const mapStateToProps = (state) => {
return {
cities: state.weather.cities,
}
}
const mapDispatchToProps = (dispatch) => {
const fetchForUpdate = (cities) => {
return cities.map((city) => {
return dispatch({ type: FETCH_START, payload: city.name })
})
}
return {
fetchForUpdate: fetchForUpdate,
}
}
const WeatherListContainer = (props) => {
const { cities } = props
const cityData = cities.map((oneCity) => {
return (
<WeatherItemContainer
name={oneCity.name}
data={oneCity.data}
key={oneCity.name}
/>
)
})
return <WeatherList item={cityData} />
}
const enhance: Function = compose(
connect(mapStateToProps, mapDispatchToProps),
lifecycle({
componentDidMount() {
console.log(this.props.cities, 'this.props.cities')
this.props.fetchForUpdate(this.props.cities)
},
}),
)
export default enhance(WeatherListContainer)
how can I fetch with redux hooks or react hooks? Or can I combine it? like use useEffect and then save it from local store to global store? Isnt it a bit ineffective?
Redux requires a middleware such as redux-thunk to dispatch asynchronous actions (an API call). If you plan on calling an API multiple times throughout your app, it makes sense to use redux-thunk and dispatch an asynchronous action, though this dispatch might still need to occur within useEffect/componentDidMount. If you only plan on a single API call, or if a specific side effect is unique to one component, there is no need to implement the middleware. For a single API call, you can send your request within useEffect/componentDidMount and then dispatch the result with a synchronous action to the redux store, without having to ever store it in component state.
https://redux.js.org/advanced/async-actions
I think there are some confusions. React hooks are used for sideEffects where redux hooks are for using the store more efficientl. Lets consider a scenario like bellow.
You are fetching a todo list from API and wanna use it all over the app. You have multiple components and you are gonna need the todo list in every component. In that case, you will call the api either using a middleware like redux-thunk or by other means like caling it in a useEffect( which is not a good practice) and save it to redux store using redux hooks. And whenever you redux store is updated, you will need to show the data in components. How will we do that? we will use react hooks to apply the sideEffects.
Here we will get the data from redux store using redux hooks. Than in a reactHooks like useEffect we will update a state of the component using useState. So here you can see, both reactHooks and reduxHooks are completely different in terms of functionality. one is storing and serving data which is reduxHooks and another one is showing the data when ever its added or updated which is reactHooks.
Hope you will find it understandable.
I am new to React, and when I was reading about the docs, I found there were two ways to implement React components, functional-based and class-based. I know before React 16.8 it's not possible to manage state in functional components, but after that there is React Hooks.
The problem is, there seems to be one restriction for React Hooks, they can only be used inside functional components. Take a server-client as an example, which needs to change an isAuthenticated state while 401 received.
//client.js
import { useUserDispatch, signOut } from "auth";
export function request(url, args) {
var dispatch = useUserDispatch();
return fetch(url, args).then(response => {
if (response.status === 401) {
logout(dispatch);
}
}
);
//auth.js
import React from "react";
var UserStateContext = React.createContext();
var UserDispatchContext = React.createContext();
function userReducer(state, action) {
...
}
function UserProvider({ children }) {
var [state, dispatch] = React.useReducer(userReducer, {
isAuthenticated: false,
});
return (
<UserStateContext.Provider value={state}>
<UserDispatchContext.Provider value={dispatch}>
{children}
</UserDispatchContext.Provider>
</UserStateContext.Provider>
);
}
function useUserState() {
return React.useContext(UserStateContext);
}
function useUserDispatch() {
return React.useContext(UserDispatchContext);
}
function signOut(dispatch) {
dispatch({});
}
export { UserProvider, useUserState, useUserDispatch, loginUser, signOut };
The client code above will produce error "Hooks can only be called inside of the body of a function component".
So maybe I have to move line var dispatch = useUserDispatch() upward to the component where request is called, and pass dispatch as props to request.
I feel this is not right, no only request is forced to care about some meaningless(to it) dispatch, but also this dispatch will spread everywhere a component needs to request.
For class-based components, this.state doesn't solve this problem either, but at least I can use mobx.
So are there some other ideal ways to solve this problem?
I came at this point too. Long story short you need to use Redux and Thunk with Async Logic, as described in detail with examples in the link below [1] if you want to do all of the stuff by hand on your own.
[1] https://redux.js.org/tutorials/essentials/part-5-async-logic
There is another solution that gives out-of-the box experience with Asynchronous API (can work with OpenAPI and GraphQL, handles request, provides caching with lifecycle, etc) wrapping stuff from [1] and its called RTK Query [2].
[2] https://redux-toolkit.js.org/rtk-query/overview
Diagram below explains [1] process visually.. but I think RTK Query [2] wraps everything in one place and could be better solution. There is a Quick Start Guide [3]. I will give it a try :-)
[3] https://redux-toolkit.js.org/tutorials/rtk-query/
Mobx and hooks are very similar in implementation. Both use a render context that is in a sense "global". React ties that render context to the component render context, but Mobx keeps that render context separate. Therefore that means that hooks have to be created within a component render lifecycle (but can sometimes be called outside that context). Mobx-react ties the Mobx render lifecycle to the react lifecycle, triggering a react re-render when observed objects change. So Mobx-react nests the react render context within the Mobx render context.
React internally keeps tracks of hooks by the number of times and order the hook is called within a component render cycle. Mobx, on the other hand, wraps any "observable" object with a proxy that lets the Mobx context know if any of its properties were referenced during a Mobx "run context" (an autorun call, essentially). Then when a property is changed, Mobx knows what "run contexts" care about that property, and re-runs those contexts. This means that anywhere you have access to an observable object you can change a property on it and Mobx will react to it.
For react state hooks, react provides a custom setter function for a state object. React then uses calls to that setter to know when it needs to re-render a component. That setter can be used anywhere, even outside a React render, but you can only create that hook inside a render call, because otherwise react has no way to tell what component to tie that hook to. Creating a hook implicitly connects it to the current render context, and that's why hooks have to be created inside render calls: hook builders have no meaning outside a render call, because they have no way to know what component they are connected to -- but once tied to a component, then they need to be available anywhere. In fact, actions like onClick or a fetch callback don't occur within a render context, although the callback is often created within that context - the action callback happens after react finishes rendering (because javascript is single threaded, so the render function must complete before anything else happens).
Hooks comes as an alternatively to class based components, you should pick up one to your project and stick to it, don't mix it up. there are some motivation for the creation of hooks, as it's better stated at docs: hook motivation.
you can create hook functions apart, but they are meant to be consumed by components. it's something like using HOC (high order component) with class based components.
const myHook = () => {
[foo, setFoo] = useState('john')
// use effect for example if you need to run something at state updates
useEffect(() => {
// do something on foo changes
}, [foo])
return [foo, setFoo] // returning state and setState you can use them by your component
}
now you have a reusable hook and you can consume at your components:
const myComponent = (props) => {
[foo, setFoo] = myHook()
const handleFoo = () => {
// some logic
setFoo(someValue)
}
return (
<div>
<span>{foo}<span>
<button onClick={handleFoo}>click</button>
</div>
)
}
obs: you should avoid declare variables as var nowadays, pick const for most, and if it's a value variable (like number) that needs update use let.
When you are creating a hooks you must refer to the Rules of Hooks
You can only call hooks from a react functions.
Don’t call Hooks from regular JavaScript functions. Instead, you can:
✅ Call Hooks from React function components.
✅ Call Hooks from custom Hooks (learn about them on this page).
If you want to create a reusable hooks then you can create a custom hooks for your functions.
You can call as many functions inside a hooks.
For example, here I'm refactoring the request function as a hook.
export function useRequest(url, args) {
var userDispatch = useUserDispatch();
const fetcher = React.useCallback(() => {
return new Promise((resolve, reject) =>
fetch(url, args)
.then((response) => {
if (response.status === 401) {
logout();
reject();
}
resolve(response);
})
.catch(reject)
);
}, [url, args]);
return [fetcher, userDispatch];
}
and then consumes it.
function App() {
const [fetch, userDispatch] = useRequest("/url", {});
React.useEffect(() => {
fetch().then((response) => {
userDispatch({ type: "USER_REQUEST", payload: response });
});
}, []);
return <div>Hello world</div>;
}
Yes, you have to use Redux or MobX to solve this problem. You have to maintain isAuthenticated state in the global state of Redux or MobX. Then make an action that could be named like, toggleAuthState and pass is to the child component and toggle the state from there.
Also you can use functional components for this case. Class based components is not mandatory to use MobX or Redux. If you maintain a HOC as a Container then you can pass the actions and states to the child.
I am showing an example of using a container as a HOC:
// Container
import React from "react"
import * as actions from "../actions"
import ChildComponent from "../components/ChildComponent"
import { connect } from "react-redux"
import { bindActionCreators } from "redux"
const Container = props => <ChildComponent { ...props } />
const mapStateToProps = state => ({ ...state })
const mapDispatchToProps = dispatch => bindActionCreators(actions, dispatch)
export default connect(mapStateToProps, mapDispatchToProps)(Container)
Then in ChildComponent you can use your states and dispatch actions whenever you need.
I'm getting my head around Redux and while I understand how it functions I'm not entirely sure if I'm using it correctly.
The Redux Documentation gives plenty of example on how to connect a functional component to my actions. But is there any way to call my action directly from within a function?
Is it possible to get something like this to work?
function mapDispatchToProps(dispatch) {
return {
saveUserData: user => dispatch(saveUserData(user))
};
}
function ConnectedUserInfo(){
console.log("fetching user info")
fetch('endpoint', 'headers',
}).then(response =>
response.then(user => {
this.props.saveUserData(user)
})
)
}
const getUserInfo = connect(
null,
mapDispatchToProps
)(ConnectedgetUserInfo);
export default getUserInfo;
I tried setting my redux state directly with saveUserData(user) but couldn't get the Store to change.
Connecting the two doesn't seem to do anything, unless I'm doing something wrong.
I'm unsure if this is the solution I'm looking for or if Redux wants me to mapDispatchToProps every time I want to change the state.
if you read the react redux documentation , you can see that connect method returns an HOC which accepts only react components.
in your code ConnectedgetUserInfo is not a react compoenent.
react-redux documentation: react-redux
react component defintion: https://reactjs.org/docs/react-component.html
also you have to name react component with starting character Capital.
I recommend instead of mapdispatch or mapstate use useDispatch and useSelector from react-redux for functional components
import {useSelector,useDispatch} from 'react-redux;
const dispatch=useDispatch();
const stateSelector=useSelector(state=>({
your states
}));
First, some context.
I'm using Redux to manage authentication state of my app and have Auth as a Redux container (or smart component).
I've created a wrapper (a higher-order component) that takes Auth and returns it:
export default function AuthWrapper(WrappedComponent) {
class Auth extends Component {
... <Auth stuff here> ...
}
return connect(mapStateToProps, mapDispatchToProps)(Auth);
}
It seems to me that in order to use the wrapper, I just need to invoke it with a component I want to have behind my auth. For example, let's say I'm authenticating a component called UserPage with the wrapper, à la:
const AuthenticatedUserPage = AuthWappper(UserPage)
However, when I use the wrapper like this, React isn't happy with me. I get the following error:
Warning: AuthenticatedApp(...): A valid React element (or null) must be returned. You may have returned undefined, an array or some other invalid object.
My best guess is that it doesn't like the connect-ified component that Redux will create when I return it from AuthWrapper... which leads me to my question:
Does React support higher-order components when those components create Redux containers? And if so, why would React be throwing this error?
Here's my two cents. I think the error is occurring elsewhere.
According to this simplified version of the connect function in react-redux, the connect function is simply returning another react component. So in your case, you're returning a component, wrapped inside another component, which is still valid. A container is basically a component.
Read https://gist.github.com/gaearon/1d19088790e70ac32ea636c025ba424e for a better understanding of the connect function.
I also tried the following in my own application and it worked.
import Layout from '../components/Layout'
//Do some other imports and stuff
function wrapper(Layout) {
return connect(null, mapDispatchToProps)(Layout);
}
export default wrapper()
Like the error states, you might just simply be returning an invalid component somewhere in your app. Your app might be throwing the error because you're not wrapping a return call in parentheses on your render method.