I am using Context API to escape prop drilling and I have created context like:
const {
Provider,
Consumer,
} = React.createContext<Context>({
carNames: [],
});
and Providing the context like:
<Provider
value={{
carNames
}}
>
{children}
</Provider>
So, to consume the context value I wanted to use useContext() BUT since I destructured Consumer and Provider out of createContext. What value should I pass to the argument of useContext(???). Tried this useContext({Consumer, Provider}) but no result 😅.
Not sure why you need to deconstruct it. Here is an working example:
App.tsx
import { ContextProvider } from "../ContextProvider";
...
const contextValue = {
carValues,
setCarValues,
};
return (
<ContextProvider.Provider value={contextValue}>
...
</ContextProvider.Provider>
);
};
ContextProvider.tsx
export interface IContextProvider {
carValues: ICarVlaues[];
setCarValues: Dispatch<SetStateAction<ICarValues[]>>;
}
export const ContextProvider = createContext<IContextProvider>({
carValues: [],
setCarValues: () => {},
});
Use it like so:
const { carValues } = useContext(ContextProvider);
Related
It's possible to pass all the props of the page to all its children components implicitly (without passing as parameter)?
I need something like this:
export default function Home({ user }) {
if (!user) {
return (
<>
<component1/>
<component2/>
<component3/>
</>
);
} else {
return (
<></>
);
}
}
export async function getServerSideProps(context) {
const { Auth } = withSSRContext(context);
try {
const user = await Auth.currentAuthenticatedUser();
return {
props: {
user: JSON.parse(JSON.stringify(user)),
}
}
}
I need that user is available to component1, component2, component3 and all its sub-components without passing explicitly.
I've read that you can use context for this. But I'm using amplify aws and I don't know if it's possible ...
First your components should be capitalize.
You can use context to pass the values without the use of the props.
For that you need to setup context using createContext
import { createContext } from "react";
const UserContext = createContext()
export default function Home({ user }) {
if (user) {
return (
<UserContext.Provider value={user}>
<Component1/>
<Component2/>
<Component3/>
</UserContext.Provider>
);
} else {
return (
<></>
);
}}
And then inside the Component1 or 2 or 3 ... You can use useContext to get the value.
import { useContext } from "react"
function Component1() {
const user = useContext(UserContext);
return (
<>
<h1>Component 1</h1>
<h2>{`Hello ${user} again!`}</h2>
</>
);
}
You can use react context, redux, recoil. Recoil is easy to use.
Context provides a way to pass data through the component tree without having to pass props down manually at every level, It's react concept, AWS Amplify will not restrict from using this. Feel free to use it here.
I'm trying to make a permissions provider that wraps some react-redux global state. I have as follows:
import React, { useCallback } from 'react';
import { useSelector } from 'react-redux';
import { createSelector } from 'reselect';
export const PermissionsContext = React.createContext();
const getUserAbilities = createSelector(
state => state.user.abilities,
abilities =>
abilities.reduce((acc, val) => {
acc[val] = true;
return acc;
}, {})
);
function useAbilities() {
const abilities = useSelector(getUserAbilities);
return { abilities };
}
export const PermissionsProvider = ({ children }) => {
const { abilities } = useAbilities();
const can = useCallback((...permissions) => permissions.every(permission => permission in abilities), [
abilities
]);
return <PermissionsContext.Provider value={{ can }}>{children}</PermissionsContext.Provider>;
};
export const withPermissions = WrappedComponent => {
return class ComponentWithPermissions extends React.Component {
render() {
return (
<PermissionsContext.Consumer>
{props => <WrappedComponent {...this.props} permissions={props} />}
</PermissionsContext.Consumer>
);
}
};
};
Usage of PermissionsProvider:
<PermissionsProvider>
<App />
</PermissionsProvider>
This includes a context so I can useContext(PermissionsContext) and also a HOC withPermissions so that I wrap legacy class components with it.
In the case of a class, I would call this.props.permissions.can('doThing1', 'doThing2') and it should return true or false depending on whether all of those abilities are present in the user payload.
It seems to be functioning fine except when I try to commit it, I get the error:
React Hook "useSelector" is called in function "can" which is neither a React function component or a custom React Hook function react-hooks/rules-of-hooks
I saw a few issues with naming convention, but that doesn't seem to apply here(?). I also used to have the useAbilities hook inside the function just above the can function which also threw the error.
Any ideas?
All the above code was correct. It seemed to be some sort of eslint cache that was continuing to complain. After clearing cache and rerunning lint it went away.
I am developing a new app using the new React Context API instead of Redux, and before, with Redux, when I needed to get a list of users for example, I simply call in componentDidMount my action, but now with React Context, my actions live inside my Consumer which is inside my render function, which means that every time my render function is called, it will call my action to get my users list and that is not good because I will be doing a lot of unecessary requests.
So, how I can call only one time my action, like in componentDidMount instead of calling in render?
Just to exemplify, look at this code:
Let's suppose that I am wrapping all my Providers in one component, like this:
import React from 'react';
import UserProvider from './UserProvider';
import PostProvider from './PostProvider';
export default class Provider extends React.Component {
render(){
return(
<UserProvider>
<PostProvider>
{this.props.children}
</PostProvider>
</UserProvider>
)
}
}
Then I put this Provider component wrapping all my app, like this:
import React from 'react';
import Provider from './providers/Provider';
import { Router } from './Router';
export default class App extends React.Component {
render() {
const Component = Router();
return(
<Provider>
<Component />
</Provider>
)
}
}
Now, at my users view for example, it will be something like this:
import React from 'react';
import UserContext from '../contexts/UserContext';
export default class Users extends React.Component {
render(){
return(
<UserContext.Consumer>
{({getUsers, users}) => {
getUsers();
return(
<h1>Users</h1>
<ul>
{users.map(user) => (
<li>{user.name}</li>
)}
</ul>
)
}}
</UserContext.Consumer>
)
}
}
What I want is this:
import React from 'react';
import UserContext from '../contexts/UserContext';
export default class Users extends React.Component {
componentDidMount(){
this.props.getUsers();
}
render(){
return(
<UserContext.Consumer>
{({users}) => {
getUsers();
return(
<h1>Users</h1>
<ul>
{users.map(user) => (
<li>{user.name}</li>
)}
</ul>
)
}}
</UserContext.Consumer>
)
}
}
But ofcourse that the example above don't work because the getUsers don't live in my Users view props. What is the right way to do it if this is possible at all?
EDIT: With the introduction of react-hooks in v16.8.0, you can use context in functional components by making use of useContext hook
const Users = () => {
const contextValue = useContext(UserContext);
// rest logic here
}
EDIT: From version 16.6.0 onwards. You can make use of context in lifecycle method using this.context like
class Users extends React.Component {
componentDidMount() {
let value = this.context;
/* perform a side-effect at mount using the value of UserContext */
}
componentDidUpdate() {
let value = this.context;
/* ... */
}
componentWillUnmount() {
let value = this.context;
/* ... */
}
render() {
let value = this.context;
/* render something based on the value of UserContext */
}
}
Users.contextType = UserContext; // This part is important to access context values
Prior to version 16.6.0, you could do it in the following manner
In order to use Context in your lifecyle method, you would write your component like
class Users extends React.Component {
componentDidMount(){
this.props.getUsers();
}
render(){
const { users } = this.props;
return(
<h1>Users</h1>
<ul>
{users.map(user) => (
<li>{user.name}</li>
)}
</ul>
)
}
}
export default props => ( <UserContext.Consumer>
{({users, getUsers}) => {
return <Users {...props} users={users} getUsers={getUsers} />
}}
</UserContext.Consumer>
)
Generally you would maintain one context in your App and it makes sense to package the above login in an HOC so as to reuse it. You can write it like
import UserContext from 'path/to/UserContext';
const withUserContext = Component => {
return props => {
return (
<UserContext.Consumer>
{({users, getUsers}) => {
return <Component {...props} users={users} getUsers={getUsers} />;
}}
</UserContext.Consumer>
);
};
};
and then you can use it like
export default withUserContext(User);
Ok, I found a way to do this with a limitation. With the with-context library I managed to insert all my consumer data into my component props.
But, to insert more than one consumer into the same component is complicated to do, you have to create mixed consumers with this library, which makes not elegant the code and non productive.
The link to this library: https://github.com/SunHuawei/with-context
EDIT: Actually you don't need to use the multi context api that with-context provide, in fact, you can use the simple api and make a decorator for each of your context and if you want to use more than one consumer in you component, just declare above your class as much decorators as you want!
For my part it was enough to add .bind(this) to the event. This is how my Component looks like.
// Stores File
class RootStore {
//...States, etc
}
const myRootContext = React.createContext(new RootStore())
export default myRootContext;
// In Component
class MyComp extends Component {
static contextType = myRootContext;
doSomething() {
console.log()
}
render() {
return <button onClick={this.doSomething.bind(this)}></button>
}
}
The following is working for me. This is a HOC that uses useContext and useReducer hooks. There's also a way to interact with sockets in this example.
I'm creating 2 contexts (one for dispatch and one for state). You would first need to wrap some outer component with the SampleProvider HOC. Then by using one or more of the utility functions, you can gain access to the state and/or the dispatch. The withSampleContext is nice because it passes both the dispatch and state. There are also other functions like useSampleState and useSampleDispatch that can be used within a functional component.
This approach allows you to code your React components as you always have without needing to inject any Context specific syntax.
import React, { useEffect, useReducer } from 'react';
import { Client } from '#stomp/stompjs';
import * as SockJS from 'sockjs-client';
const initialState = {
myList: [],
myObject: {}
};
export const SampleStateContext = React.createContext(initialState);
export const SampleDispatchContext = React.createContext(null);
const ACTION_TYPE = {
SET_MY_LIST: 'SET_MY_LIST',
SET_MY_OBJECT: 'SET_MY_OBJECT'
};
const sampleReducer = (state, action) => {
switch (action.type) {
case ACTION_TYPE.SET_MY_LIST:
return {
...state,
myList: action.myList
};
case ACTION_TYPE.SET_MY_OBJECT:
return {
...state,
myObject: action.myObject
};
default: {
throw new Error(`Unhandled action type: ${action.type}`);
}
}
};
/**
* Provider wrapper that also initializes reducer and socket communication
* #param children
* #constructor
*/
export const SampleProvider = ({ children }: any) => {
const [state, dispatch] = useReducer(sampleReducer, initialState);
useEffect(() => initializeSocket(dispatch), [initializeSocket]);
return (
<SampleStateContext.Provider value={state}>
<SampleDispatchContext.Provider value={dispatch}>{children}</SampleDispatchContext.Provider>
</SampleStateContext.Provider>
);
};
/**
* HOC function used to wrap component with both state and dispatch contexts
* #param Component
*/
export const withSampleContext = Component => {
return props => {
return (
<SampleDispatchContext.Consumer>
{dispatch => (
<SampleStateContext.Consumer>
{contexts => <Component {...props} {...contexts} dispatch={dispatch} />}
</SampleStateContext.Consumer>
)}
</SampleDispatchContext.Consumer>
);
};
};
/**
* Use this within a react functional component if you want state
*/
export const useSampleState = () => {
const context = React.useContext(SampleStateContext);
if (context === undefined) {
throw new Error('useSampleState must be used within a SampleProvider');
}
return context;
};
/**
* Use this within a react functional component if you want the dispatch
*/
export const useSampleDispatch = () => {
const context = React.useContext(SampleDispatchContext);
if (context === undefined) {
throw new Error('useSampleDispatch must be used within a SampleProvider');
}
return context;
};
/**
* Sample function that can be imported to set state via dispatch
* #param dispatch
* #param obj
*/
export const setMyObject = async (dispatch, obj) => {
dispatch({ type: ACTION_TYPE.SET_MY_OBJECT, myObject: obj });
};
/**
* Initialize socket and any subscribers
* #param dispatch
*/
const initializeSocket = dispatch => {
const client = new Client({
brokerURL: 'ws://path-to-socket:port',
debug: function (str) {
console.log(str);
},
reconnectDelay: 5000,
heartbeatIncoming: 4000,
heartbeatOutgoing: 4000
});
// Fallback code for http(s)
if (typeof WebSocket !== 'function') {
client.webSocketFactory = function () {
return new SockJS('https://path-to-socket:port');
};
}
const onMessage = msg => {
dispatch({ type: ACTION_TYPE.SET_MY_LIST, myList: JSON.parse(msg.body) });
};
client.onConnect = function (frame) {
client.subscribe('/topic/someTopic', onMessage);
};
client.onStompError = function (frame) {
console.log('Broker reported error: ' + frame.headers['message']);
console.log('Additional details: ' + frame.body);
};
client.activate();
};
You have to pass context in higher parent component to get access as a props in child.
I am developing a new app using the new React Context API instead of Redux, and before, with Redux, when I needed to get a list of users for example, I simply call in componentDidMount my action, but now with React Context, my actions live inside my Consumer which is inside my render function, which means that every time my render function is called, it will call my action to get my users list and that is not good because I will be doing a lot of unecessary requests.
So, how I can call only one time my action, like in componentDidMount instead of calling in render?
Just to exemplify, look at this code:
Let's suppose that I am wrapping all my Providers in one component, like this:
import React from 'react';
import UserProvider from './UserProvider';
import PostProvider from './PostProvider';
export default class Provider extends React.Component {
render(){
return(
<UserProvider>
<PostProvider>
{this.props.children}
</PostProvider>
</UserProvider>
)
}
}
Then I put this Provider component wrapping all my app, like this:
import React from 'react';
import Provider from './providers/Provider';
import { Router } from './Router';
export default class App extends React.Component {
render() {
const Component = Router();
return(
<Provider>
<Component />
</Provider>
)
}
}
Now, at my users view for example, it will be something like this:
import React from 'react';
import UserContext from '../contexts/UserContext';
export default class Users extends React.Component {
render(){
return(
<UserContext.Consumer>
{({getUsers, users}) => {
getUsers();
return(
<h1>Users</h1>
<ul>
{users.map(user) => (
<li>{user.name}</li>
)}
</ul>
)
}}
</UserContext.Consumer>
)
}
}
What I want is this:
import React from 'react';
import UserContext from '../contexts/UserContext';
export default class Users extends React.Component {
componentDidMount(){
this.props.getUsers();
}
render(){
return(
<UserContext.Consumer>
{({users}) => {
getUsers();
return(
<h1>Users</h1>
<ul>
{users.map(user) => (
<li>{user.name}</li>
)}
</ul>
)
}}
</UserContext.Consumer>
)
}
}
But ofcourse that the example above don't work because the getUsers don't live in my Users view props. What is the right way to do it if this is possible at all?
EDIT: With the introduction of react-hooks in v16.8.0, you can use context in functional components by making use of useContext hook
const Users = () => {
const contextValue = useContext(UserContext);
// rest logic here
}
EDIT: From version 16.6.0 onwards. You can make use of context in lifecycle method using this.context like
class Users extends React.Component {
componentDidMount() {
let value = this.context;
/* perform a side-effect at mount using the value of UserContext */
}
componentDidUpdate() {
let value = this.context;
/* ... */
}
componentWillUnmount() {
let value = this.context;
/* ... */
}
render() {
let value = this.context;
/* render something based on the value of UserContext */
}
}
Users.contextType = UserContext; // This part is important to access context values
Prior to version 16.6.0, you could do it in the following manner
In order to use Context in your lifecyle method, you would write your component like
class Users extends React.Component {
componentDidMount(){
this.props.getUsers();
}
render(){
const { users } = this.props;
return(
<h1>Users</h1>
<ul>
{users.map(user) => (
<li>{user.name}</li>
)}
</ul>
)
}
}
export default props => ( <UserContext.Consumer>
{({users, getUsers}) => {
return <Users {...props} users={users} getUsers={getUsers} />
}}
</UserContext.Consumer>
)
Generally you would maintain one context in your App and it makes sense to package the above login in an HOC so as to reuse it. You can write it like
import UserContext from 'path/to/UserContext';
const withUserContext = Component => {
return props => {
return (
<UserContext.Consumer>
{({users, getUsers}) => {
return <Component {...props} users={users} getUsers={getUsers} />;
}}
</UserContext.Consumer>
);
};
};
and then you can use it like
export default withUserContext(User);
Ok, I found a way to do this with a limitation. With the with-context library I managed to insert all my consumer data into my component props.
But, to insert more than one consumer into the same component is complicated to do, you have to create mixed consumers with this library, which makes not elegant the code and non productive.
The link to this library: https://github.com/SunHuawei/with-context
EDIT: Actually you don't need to use the multi context api that with-context provide, in fact, you can use the simple api and make a decorator for each of your context and if you want to use more than one consumer in you component, just declare above your class as much decorators as you want!
For my part it was enough to add .bind(this) to the event. This is how my Component looks like.
// Stores File
class RootStore {
//...States, etc
}
const myRootContext = React.createContext(new RootStore())
export default myRootContext;
// In Component
class MyComp extends Component {
static contextType = myRootContext;
doSomething() {
console.log()
}
render() {
return <button onClick={this.doSomething.bind(this)}></button>
}
}
The following is working for me. This is a HOC that uses useContext and useReducer hooks. There's also a way to interact with sockets in this example.
I'm creating 2 contexts (one for dispatch and one for state). You would first need to wrap some outer component with the SampleProvider HOC. Then by using one or more of the utility functions, you can gain access to the state and/or the dispatch. The withSampleContext is nice because it passes both the dispatch and state. There are also other functions like useSampleState and useSampleDispatch that can be used within a functional component.
This approach allows you to code your React components as you always have without needing to inject any Context specific syntax.
import React, { useEffect, useReducer } from 'react';
import { Client } from '#stomp/stompjs';
import * as SockJS from 'sockjs-client';
const initialState = {
myList: [],
myObject: {}
};
export const SampleStateContext = React.createContext(initialState);
export const SampleDispatchContext = React.createContext(null);
const ACTION_TYPE = {
SET_MY_LIST: 'SET_MY_LIST',
SET_MY_OBJECT: 'SET_MY_OBJECT'
};
const sampleReducer = (state, action) => {
switch (action.type) {
case ACTION_TYPE.SET_MY_LIST:
return {
...state,
myList: action.myList
};
case ACTION_TYPE.SET_MY_OBJECT:
return {
...state,
myObject: action.myObject
};
default: {
throw new Error(`Unhandled action type: ${action.type}`);
}
}
};
/**
* Provider wrapper that also initializes reducer and socket communication
* #param children
* #constructor
*/
export const SampleProvider = ({ children }: any) => {
const [state, dispatch] = useReducer(sampleReducer, initialState);
useEffect(() => initializeSocket(dispatch), [initializeSocket]);
return (
<SampleStateContext.Provider value={state}>
<SampleDispatchContext.Provider value={dispatch}>{children}</SampleDispatchContext.Provider>
</SampleStateContext.Provider>
);
};
/**
* HOC function used to wrap component with both state and dispatch contexts
* #param Component
*/
export const withSampleContext = Component => {
return props => {
return (
<SampleDispatchContext.Consumer>
{dispatch => (
<SampleStateContext.Consumer>
{contexts => <Component {...props} {...contexts} dispatch={dispatch} />}
</SampleStateContext.Consumer>
)}
</SampleDispatchContext.Consumer>
);
};
};
/**
* Use this within a react functional component if you want state
*/
export const useSampleState = () => {
const context = React.useContext(SampleStateContext);
if (context === undefined) {
throw new Error('useSampleState must be used within a SampleProvider');
}
return context;
};
/**
* Use this within a react functional component if you want the dispatch
*/
export const useSampleDispatch = () => {
const context = React.useContext(SampleDispatchContext);
if (context === undefined) {
throw new Error('useSampleDispatch must be used within a SampleProvider');
}
return context;
};
/**
* Sample function that can be imported to set state via dispatch
* #param dispatch
* #param obj
*/
export const setMyObject = async (dispatch, obj) => {
dispatch({ type: ACTION_TYPE.SET_MY_OBJECT, myObject: obj });
};
/**
* Initialize socket and any subscribers
* #param dispatch
*/
const initializeSocket = dispatch => {
const client = new Client({
brokerURL: 'ws://path-to-socket:port',
debug: function (str) {
console.log(str);
},
reconnectDelay: 5000,
heartbeatIncoming: 4000,
heartbeatOutgoing: 4000
});
// Fallback code for http(s)
if (typeof WebSocket !== 'function') {
client.webSocketFactory = function () {
return new SockJS('https://path-to-socket:port');
};
}
const onMessage = msg => {
dispatch({ type: ACTION_TYPE.SET_MY_LIST, myList: JSON.parse(msg.body) });
};
client.onConnect = function (frame) {
client.subscribe('/topic/someTopic', onMessage);
};
client.onStompError = function (frame) {
console.log('Broker reported error: ' + frame.headers['message']);
console.log('Additional details: ' + frame.body);
};
client.activate();
};
You have to pass context in higher parent component to get access as a props in child.
I am developing a new app using the new React Context API instead of Redux, and before, with Redux, when I needed to get a list of users for example, I simply call in componentDidMount my action, but now with React Context, my actions live inside my Consumer which is inside my render function, which means that every time my render function is called, it will call my action to get my users list and that is not good because I will be doing a lot of unecessary requests.
So, how I can call only one time my action, like in componentDidMount instead of calling in render?
Just to exemplify, look at this code:
Let's suppose that I am wrapping all my Providers in one component, like this:
import React from 'react';
import UserProvider from './UserProvider';
import PostProvider from './PostProvider';
export default class Provider extends React.Component {
render(){
return(
<UserProvider>
<PostProvider>
{this.props.children}
</PostProvider>
</UserProvider>
)
}
}
Then I put this Provider component wrapping all my app, like this:
import React from 'react';
import Provider from './providers/Provider';
import { Router } from './Router';
export default class App extends React.Component {
render() {
const Component = Router();
return(
<Provider>
<Component />
</Provider>
)
}
}
Now, at my users view for example, it will be something like this:
import React from 'react';
import UserContext from '../contexts/UserContext';
export default class Users extends React.Component {
render(){
return(
<UserContext.Consumer>
{({getUsers, users}) => {
getUsers();
return(
<h1>Users</h1>
<ul>
{users.map(user) => (
<li>{user.name}</li>
)}
</ul>
)
}}
</UserContext.Consumer>
)
}
}
What I want is this:
import React from 'react';
import UserContext from '../contexts/UserContext';
export default class Users extends React.Component {
componentDidMount(){
this.props.getUsers();
}
render(){
return(
<UserContext.Consumer>
{({users}) => {
getUsers();
return(
<h1>Users</h1>
<ul>
{users.map(user) => (
<li>{user.name}</li>
)}
</ul>
)
}}
</UserContext.Consumer>
)
}
}
But ofcourse that the example above don't work because the getUsers don't live in my Users view props. What is the right way to do it if this is possible at all?
EDIT: With the introduction of react-hooks in v16.8.0, you can use context in functional components by making use of useContext hook
const Users = () => {
const contextValue = useContext(UserContext);
// rest logic here
}
EDIT: From version 16.6.0 onwards. You can make use of context in lifecycle method using this.context like
class Users extends React.Component {
componentDidMount() {
let value = this.context;
/* perform a side-effect at mount using the value of UserContext */
}
componentDidUpdate() {
let value = this.context;
/* ... */
}
componentWillUnmount() {
let value = this.context;
/* ... */
}
render() {
let value = this.context;
/* render something based on the value of UserContext */
}
}
Users.contextType = UserContext; // This part is important to access context values
Prior to version 16.6.0, you could do it in the following manner
In order to use Context in your lifecyle method, you would write your component like
class Users extends React.Component {
componentDidMount(){
this.props.getUsers();
}
render(){
const { users } = this.props;
return(
<h1>Users</h1>
<ul>
{users.map(user) => (
<li>{user.name}</li>
)}
</ul>
)
}
}
export default props => ( <UserContext.Consumer>
{({users, getUsers}) => {
return <Users {...props} users={users} getUsers={getUsers} />
}}
</UserContext.Consumer>
)
Generally you would maintain one context in your App and it makes sense to package the above login in an HOC so as to reuse it. You can write it like
import UserContext from 'path/to/UserContext';
const withUserContext = Component => {
return props => {
return (
<UserContext.Consumer>
{({users, getUsers}) => {
return <Component {...props} users={users} getUsers={getUsers} />;
}}
</UserContext.Consumer>
);
};
};
and then you can use it like
export default withUserContext(User);
Ok, I found a way to do this with a limitation. With the with-context library I managed to insert all my consumer data into my component props.
But, to insert more than one consumer into the same component is complicated to do, you have to create mixed consumers with this library, which makes not elegant the code and non productive.
The link to this library: https://github.com/SunHuawei/with-context
EDIT: Actually you don't need to use the multi context api that with-context provide, in fact, you can use the simple api and make a decorator for each of your context and if you want to use more than one consumer in you component, just declare above your class as much decorators as you want!
For my part it was enough to add .bind(this) to the event. This is how my Component looks like.
// Stores File
class RootStore {
//...States, etc
}
const myRootContext = React.createContext(new RootStore())
export default myRootContext;
// In Component
class MyComp extends Component {
static contextType = myRootContext;
doSomething() {
console.log()
}
render() {
return <button onClick={this.doSomething.bind(this)}></button>
}
}
The following is working for me. This is a HOC that uses useContext and useReducer hooks. There's also a way to interact with sockets in this example.
I'm creating 2 contexts (one for dispatch and one for state). You would first need to wrap some outer component with the SampleProvider HOC. Then by using one or more of the utility functions, you can gain access to the state and/or the dispatch. The withSampleContext is nice because it passes both the dispatch and state. There are also other functions like useSampleState and useSampleDispatch that can be used within a functional component.
This approach allows you to code your React components as you always have without needing to inject any Context specific syntax.
import React, { useEffect, useReducer } from 'react';
import { Client } from '#stomp/stompjs';
import * as SockJS from 'sockjs-client';
const initialState = {
myList: [],
myObject: {}
};
export const SampleStateContext = React.createContext(initialState);
export const SampleDispatchContext = React.createContext(null);
const ACTION_TYPE = {
SET_MY_LIST: 'SET_MY_LIST',
SET_MY_OBJECT: 'SET_MY_OBJECT'
};
const sampleReducer = (state, action) => {
switch (action.type) {
case ACTION_TYPE.SET_MY_LIST:
return {
...state,
myList: action.myList
};
case ACTION_TYPE.SET_MY_OBJECT:
return {
...state,
myObject: action.myObject
};
default: {
throw new Error(`Unhandled action type: ${action.type}`);
}
}
};
/**
* Provider wrapper that also initializes reducer and socket communication
* #param children
* #constructor
*/
export const SampleProvider = ({ children }: any) => {
const [state, dispatch] = useReducer(sampleReducer, initialState);
useEffect(() => initializeSocket(dispatch), [initializeSocket]);
return (
<SampleStateContext.Provider value={state}>
<SampleDispatchContext.Provider value={dispatch}>{children}</SampleDispatchContext.Provider>
</SampleStateContext.Provider>
);
};
/**
* HOC function used to wrap component with both state and dispatch contexts
* #param Component
*/
export const withSampleContext = Component => {
return props => {
return (
<SampleDispatchContext.Consumer>
{dispatch => (
<SampleStateContext.Consumer>
{contexts => <Component {...props} {...contexts} dispatch={dispatch} />}
</SampleStateContext.Consumer>
)}
</SampleDispatchContext.Consumer>
);
};
};
/**
* Use this within a react functional component if you want state
*/
export const useSampleState = () => {
const context = React.useContext(SampleStateContext);
if (context === undefined) {
throw new Error('useSampleState must be used within a SampleProvider');
}
return context;
};
/**
* Use this within a react functional component if you want the dispatch
*/
export const useSampleDispatch = () => {
const context = React.useContext(SampleDispatchContext);
if (context === undefined) {
throw new Error('useSampleDispatch must be used within a SampleProvider');
}
return context;
};
/**
* Sample function that can be imported to set state via dispatch
* #param dispatch
* #param obj
*/
export const setMyObject = async (dispatch, obj) => {
dispatch({ type: ACTION_TYPE.SET_MY_OBJECT, myObject: obj });
};
/**
* Initialize socket and any subscribers
* #param dispatch
*/
const initializeSocket = dispatch => {
const client = new Client({
brokerURL: 'ws://path-to-socket:port',
debug: function (str) {
console.log(str);
},
reconnectDelay: 5000,
heartbeatIncoming: 4000,
heartbeatOutgoing: 4000
});
// Fallback code for http(s)
if (typeof WebSocket !== 'function') {
client.webSocketFactory = function () {
return new SockJS('https://path-to-socket:port');
};
}
const onMessage = msg => {
dispatch({ type: ACTION_TYPE.SET_MY_LIST, myList: JSON.parse(msg.body) });
};
client.onConnect = function (frame) {
client.subscribe('/topic/someTopic', onMessage);
};
client.onStompError = function (frame) {
console.log('Broker reported error: ' + frame.headers['message']);
console.log('Additional details: ' + frame.body);
};
client.activate();
};
You have to pass context in higher parent component to get access as a props in child.