Develop Reference

this.props Not Returning Fetched Data From Parent Component (React)

I am attempting to render playlist information for an Audio Player in React. The data is coming from a fetch call in the parent component (PostContent.js). The data being returned is an array of objects that looks like:
[ {name: ‘track name’, artist: ‘artist name’, url: ’https://blahblah.wav', lrc: ‘string’, theme: ‘another string’ }, {…}, {…}, etc. }
I am not able to return the data in the render() method of the child component (AudioPlayer.js). When I console.log(this.props.audio) in the render(), my terminal prints three responses. The first is an empty array, and the next two are the correct data that I need (an array of objects).
How can I set the props on the ‘audio’ key in the ‘props’ object in the render() method of the AudioPlayer.js component?
I should mention that I am using the react-aplayer library, and I am able to make this work with hard-coded data, as in the example here (https://github.com/MoePlayer/react-aplayer), but I am trying to make a dynamic playlist component for a blog website. Any advice is greatly appreciated.
AudioPlayer.js (Child Component)
import React, { PureComponent, Fragment } from 'react';
import ReactAplayer from '../react-aplayer';
import './AudioPlayer.css';
import sample from '../../src/adrian_trinkhaus.jpeg';
export default class AudioPlayer extends React.Component {
// event binding example
onPlay = () => {
console.log('on play');
};
onPause = () => {
console.log('on pause');
};
// example of access aplayer instance
onInit = ap => {
this.ap = ap;
};
render() {
console.log('props in render of AudioPlayer', this.props.audio)
const props = {
theme: '#F57F17',
lrcType: 3,
audio: this.props.audio
};
return (
<div>
<ReactAplayer
{...props}
onInit={this.onInit}
onPlay={this.onPlay}
onPause={this.onPause}
/>
</div>
);
}
}
PostContent.js (Parent Component)
import React, { Component, useState, Fragment } from 'react';
import { BrowserRouter as Router, Route, Link } from 'react-router-dom';
import AudioPlayer from './AudioPlayer';
export default class PostContent extends Component {
constructor(props) {
super(props);
this.state = {
id: '',
episodeData: [],
audio: []
}
}
async componentDidMount() {
const { id } = this.props.match.params;
const response = await fetch(`http://localhost:5000/episode/${id}/playlist`);
const jsonData = await response.json();
const songs = jsonData;
const audio = Object.keys(songs).map(key => {
return {
name: songs[key].name,
artist: songs[key].artist,
url: songs[key].url,
cover: songs[key].cover,
lrc: songs[key].lrc,
theme: songs[key].theme
}
});
this.setState({ audio })
}
componentDidUpdate(prevProps, prevState) {
if (prevState.audio !== this.state.audio) {
const newAudio = this.state.audio;
this.setState({ audio: newAudio }, () => console.log('new audio', this.state.audio))
}
}
render() {
return (
<Fragment>
<AudioPlayer audio={this.state.audio} />
<Link id='home-link' to='/' activeClassName='active'>Homepage</Link>
{this.state.episodeData.map((item, i) => (
<div key={i} className="word-content">
<h2 className="show-title">{item.post_title}</h2>
<div className="episode-post-content">
<p>{item.post_content1}</p>
<p>{item.post_content2}</p>
<p>{item.post_content3}</p></div>
</div>
))}
<Table data={this.state.data} />
<div className="bottom-link">
<Link id='home-link' to='/' activeClassName='active'>Homepage</Link>
</div>
</Fragment>
)
}
}

i played around with an async scenario with your code on codesandbox
i think the problem is when you're trying to access the payload in ReactAPlayer component when audio it's not loaded yet from the async call. what you need to do is only use "audio" when it's valid like this if (audio.length) {...} or audio && ... some form of check to prevent it from being accessed in the reactAplayer render function.
fyi - you can remove the componentDidUpdate hook, since you have a setState call inside the ...Didmount hook, when setState is called inside ...didMount, the component calls its render() thus trigger a child re-render and its child will do the same..

Actually I think it doesnt work because you set this.props inside a props obejct, so maybe you need to do something like
var that = this
const props = {
audio = that.props.audio
}

Child component does not load event of parent component in React

I creating chat application by React.
In the chat application, there is a field for entering user_name and text.
I thought about managing those data with state, I made onNameChange and onTextChange events.
However, in the code I created, onTextChange was loaded but onNameChange was not loaded.
I know that onTextChange in the same file will be loaded.
Even though the files are different, I thought that data can be exchanged via props if the relationship is between parent and child.
I described the code with such a recognition, but I could not get the results I expected.
How can I pass data from LogoutStateForm.js to user_name in ChatForm.js via onNameChange?
ChatForm.js
import React,{Component} from 'react'
import firebase from 'firebase/app'
import { firebaseApp,firebaseDB } from '../firebase/firebase'
import LogoutStateForm from './LogoutStateForm'
const messagesRef = firebaseDB.ref('messages')
class ChatForm extends Component {
constructor(props){
super(props)
this.onNameChange = this.onNameChange.bind(this)
this.onTextChange = this.onTextChange.bind(this)
this.state = {
user: null,
user_name: "",
text: ""
}
}
componentDidMount(){
firebase.auth().onAuthStateChanged(user => {
this.setState({ user })
})
}
onNameChange(e) {
if (e.target.name == 'user_name') {
this.setState({
user_name: e.target.value
}),
console.log(this.state.user_name);
}
}
onTextChange(e) {
if (e.target.name == 'text') {
this.setState({
text: e.target.value
}),
console.log(this.state.text);
}
}
render(){
return(
<div id='Form'>
{this.state.user ?
<LogoutStateForm onClick={this.onNameChange} />:
null
}
//In order to switch display depending on login availability
<textarea name='text' onChange={this.onTextChange} placeholder='メッセージ'/>
</div>
)
}
}
export default ChatForm
LogoutStateForm.js
import React,{Component} from 'react'
import firebase from 'firebase/app'
class LogoutStateForm extends Component {
constructor(props){
super(props)
}
login() {
const provider = new firebase.auth.GoogleAuthProvider()
firebase.auth().signInWithPopup(provider)
}
componentDidMount(){
firebase.auth().onAuthStateChanged(user => {
this.setState({ user })
})
}
render(){
return(
<div className='logout'>
<input name='user_name' onChange={this.props.onNameChange} placeholder='名前'/>
<button onClick={this.login}>Goggle Login</button>
</div>
)
}
}
export default LogoutStateForm
Please lend me your wisdom.
Thank you.

First, in ChatForm.js, what you render LoginStateForm not LogoutStateForm.
Second, assuming it's supposed to be LogoutStateForm, at ChatForm component you pass onNameChange as onClick to LogoutStateForm.
However, you access the props as onNameChange in LogoutStateForm which is wrong. You should access it as the props name that you give, which is this.props.onClick.
Hope it helps.

In ChatForm.js, you are rendering wrong component, It should be LogoutStateForm.
Second you should access prop which you have passed.
ChatForm.js
<LogoutStateForm onNameChange={this.onNameChange} />
In LogoutStateForm.js
render(){
return(
<div className='logout'>
<input name='user_name' onChange={this.props.onNameChange} placeholder='名前'/>
<button onClick={this.login}>Goggle Login</button>
</div>
)
}
Also, define PropTypes in LogoutStateForm.js for verifying type check.
https://reactjs.org/docs/typechecking-with-proptypes.html

Rendering a canvas object received from props

Good day!
I am new to React and html2canvas. I am making an app which will take "screenshots" of my DOM using html2canvas then store it to an array of screenshots which will then be also rendered on the screen.
I am storing each <canvas> object received from the html2canvas promise to an array then pass it to my ScreenshotsContainer component which passes the array to the Screenshots component. The Screenshots component will then map the array of <canvas> objects to individual Screenshot components.
In App.js, I am calling the html2canvas function then pass the array to ScreenshotsContainer component
import React, { Component } from 'react';
import ScreenshotsContainer from './containers/ScreenshotsContainer/ScreenshotsContainer'
import html2canvas from 'html2canvas';
import './App.css';
class App extends Component {
state = {
canvasArray: []
}
getScreenshotHandler = () => {
console.log("[Canvas Array from state length:]" + this.state.canvasArray.length)
let canvasArray = this.state.canvasArray;
html2canvas(document.body).then((canvas) => {
canvasArray.push(canvas)
});
console.log("[Canvas Object value: ]" + canvasArray);
this.setState({ canvasArray: canvasArray })
}
render() {
return (
<React.Fragment>
<button onClick={this.getScreenshotHandler}>Get Screenshot</button>
<ScreenshotsContainer canvasArray={this.state.canvasArray} />
</React.Fragment>
);
}
}
export default App;
The ScreenshotsContainer component will pass the received array to the Screenshots component:
import React, { Component } from 'react';
import './ScreenshotsContainer.css'
import Screenshots from '../../components/Screenshots/Screenshots';
class ScreenshotsContainer extends Component {
render() {
return (
<div className="ScreenshotsContainer">
<Screenshots canvasArray={this.props.canvasArray} />
</div>
);
}
}
export default ScreenshotsContainer;
The Screenshots component will map the array and pass each canvas object to the Screenshot component:
import React, { Component } from 'react';
import Screenshot from './Screenshot/Screenshot';
class Screenshots extends Component {
render() {
const screenshots = this.props.canvasArray.map(canvas => {
return (
<Screenshot
key={Math.random}
canvasObj={canvas}
/>
)
})
return (
<React.Fragment>
{screenshots}
</React.Fragment>
);
}
}
export default Screenshots;
Here is the Screenshot component
import React from 'react';
import './Screenshot.css';
const screenshot = (props) => (
<div className="Screenshot" >
<canvas ref={props.canvasObj} style={{
width: '10%',
height: '10%'
}} />
</div>
);
export default screenshot;
What I actually get when pressing the button:
Actual screenshot of my result
I was wondering which part went wrong. Any help would be appreciated.

This particular library works in a specific way (looks like it's doing a lot of "magic" under the hood - you should look at the source code here more specifically the renderer folder inside src)
Saving the canvas to the state inside of an array (the correct react way of doing things) will be a problem as it saves it as a complex object with many methods etc... and we can not render objects... This lib was not written with React in mind...
The code sample below is a simple implementation in React...
Here is a live demo: https://codesandbox.io/s/9y24vwn1py
import React, { Component } from 'react';
import html2canvas from 'html2canvas';
class App extends Component {
constructor(props) {
super(props);
this.captureRef = React.createRef();
this.displayRef = React.createRef();
}
getScreenshotHandler = () => {
html2canvas(this.captureRef.current).then(canvas =>
this.displayRef.current.appendChild(canvas),
);
};
render() {
return (
<div>
<div ref={this.captureRef}>
<h2>This enitre div will be captured and added to the screen</h2>
</div>
<button onClick={this.getScreenshotHandler}>Get Screenshot!</button>
<section>
<h5>Your screenshots will be availbale below</h5>
<div ref={this.displayRef} />
</section>
</div>
);
}
}
export default App;
EDIT: based on the comment below here is yet another workaround:
class App extends Component {
constructor(props) {
super(props);
this.state = { canvasArray: [] };
this.captureRef = React.createRef();
}
getScreenshotHandler = () => {
html2canvas(this.captureRef.current).then(canvas =>
this.setState({
canvasArray: [canvas.toDataURL(), ...this.state.canvasArray],
}),
);
};
renderCanvas = () => {
return this.state.canvasArray.map((canvas, i) => {
return <img key={i} src={canvas} alt="screenshot" />;
});
};
render() {
return (
<div className="wrapper">
<div ref={this.captureRef}>
<p>This enitre div will be captured</p>
</div>
<button onClick={this.getScreenshotHandler}>Get Screenshot!</button>
<section>
<h5>Your screenshots will be availbale below:</h5>
{this.renderCanvas()}
</section>
</div>
);
}
}
Link to live demo: https://codesandbox.io/s/1r213057vq

ReactJS How to pass child component values to parent component

I have below codes
chat.js
import React from 'react';
import '../styles/Chat.css';
import Web from '../services/Web';
class Chat extends React.Component {
constructor(props) {
super(props);
this.state = {
msg:''
};
this.sendMessage = this.sendMessage.bind(this);
}
sendMessage () {
this.props.updatecommentText(this.refs.newText.value, this.props.index);
this.setState({ msg: '' });
}
render() {
return (
<div className="Chat-container">
<div className="Chat-row">
<div className="Chat-column">
<div className="Chat-card">
<div className="Chat-body">
<div className="Chat-title">React Based Chatbot</div>
<div className="Chat-messages">
{ this.props.children }
</div>
</div>
<div className="Chat-footer">
<textarea className="Chat-input" ref="newText"></textarea>
<button className="Chat-submit" onClick={this.sendMessage} defaultValue={ this.props.children }>Send</button>
</div>
</div>
</div>
</div>
</div>
);
}
}
export default Chat;
Web.js
import React, { Component } from 'react';
import PropTypes from "prop-types";
import { Link } from "react-router-dom";
import Chat from '../components/Chat';
class Web extends React.Component {
constructor(props){
super(props);
this.state = {
messages:["Hi, How can I help you ?"
]
};
this.sendtobot = this.sendtobot.bind(this);
}
sendtobot(newText, i){
var arr = this.state.messages
arr.push(newText)
this.setState({messages: arr})
}
eachMessage(message, i){
return (<Chat key={i} index={i} updatecommentText={ this.sendtobot.bind(this) }>{ message }</Chat>);
}
render(){
return(
<div>
{this.state.messages.map(this.eachMessage.bind(this))}
</div>
)
}
}
export default Web;
I wanted to take the input from the Chat.js and send it to Web.js and push that value to array messages and then again render that array in the this.props.children in Chat.js
But, while running the code, I am getting an error this.props.updatecommentText is not a function.
Can someone please help me with this.

You have bind this.sendtobot twice. It should be only in the constructor.
like this
eachMessage(message, i){
return (
<Chat key={i} index={i} updatecommentText={this.sendtobot}>
{ message }
</Chat>
);
}

Your code seems to work.
Here is a sandbox with your code.
I'm not sure it works as you would expect, but it works without errors.

By changing this 3 functions in Web component, it starting to look like a chat with only one textarea
sendtobot(newText, i) {
this.setState({ messages: [...this.state.messages, newText] })
}
eachMessage(message, i) {
return (<p>{message}</p>);
}
render() {
return (
<div>
{this.state.messages.map(this.eachMessage.bind(this))}
<Chat updatecommentText={this.sendtobot}/>
</div>
)
}

You can pass child's component state to parent component using redux also as global state.

How to send this.state from a component to relay root container

I want to change my root query parameter based on the this.state.eventid which is a child component, but I have no clue how to get props to relay root container. I started based on relay-starter-kit.
I have React component that has a dropdown menu, and onSelect it setStates for eventId
renderAttend() {
if (this.props.groups != null && this.state.success != true) {
var events = this.props.events.map(function(event){
var boundSelect = () => {this.setState({eventid:event.nodes[0].id})}
return <MenuItem style={{fontSize:20}}eventKey={event.nodes[0].id} onSelect={boundSelect.bind(this)}>{event.nodes[0].properties.summary} / {event.nodes[0].properties.start}</MenuItem>
},this)
var teams = this.props.groups.map(function(team){
var boundSelect = () => {this.setState({teamid:team.nodes[0].id})}
return <MenuItem style={{fontSize:20}}eventKey={team.nodes[0].id} onSelect={boundSelect.bind(this)}>{team.nodes[0].properties.name}</MenuItem>
},this)
return (
<div>
<ButtonGroup>
<DropdownButton style={{padding:"15px",fontSize:20}}title="Events" id="bg-vertical-dropdown-2">
{events}
</DropdownButton>
<DropdownButton style={{padding:"15px",fontSize:20,marginLeft:"5px"}} title="Groups" id="bg-vertical-dropdown-2">
{teams}
</DropdownButton>
</ButtonGroup>
</div>
)
}
}
I want to use this state to somehow change my root query...
my approute...
import Relay from 'react-relay';
export default class extends Relay.Route {
static paramDefinitions = {
eventId: {required: false}
};
static queries = {
Event : () => Relay.QL`query{eventState(eventId:$eventId)}`,
};
static routeName = 'AppHomeRoute';
}
and my app.js
import 'babel-polyfill';
import App from './components/App';
import AppHomeRoute from './routes/AppHomeRoute';
import React from 'react';
import ReactDOM from 'react-dom';
import Relay from 'react-relay';
ReactDOM.render(
<Relay.RootContainer
Component={App}
route= {new AppHomeRoute}
renderLoading={function() {
return <div style= {{display:"flex",justifyContent:"center",marginTop:"55px"}}> <h1>Loading...</h1></div>;
}}
renderFailure={function(error, retry) {
return (
<div>
<h1>Click Refresh</h1>
</div>
);
}}
/>,
document.getElementById('root')
);
Now I want to this.state.eventid from the react component to update my root query, but I have no idea how to pass data from child component to react root.container. I do not want to use react-router for this :)
p.s. this.props.events were passed to me by an ajax call so they are not saved in relay/graphql data.

For such a case, the better thing to do is to wrap your root query into a story like
{
store {
events(eventId:$eventId)
}
}
So in the root query you only have
export default class extends Route {
static queries = {
app:() => Relay.QL`query { store }`
};
static routeName = "AppRoute";
}
And in the page you create a fragemnt like
let RelayApp = createContainer(SomeComponent, {
initialVariables: {
eventId: null
},
fragments: {
app: () => Relay.QL `
fragment on Store {
id
events(eventId: $eventId) {
pageInfo {
hasNextPage
}
edges {
cursor
node {
name
...
}
}
}
}
`,
},
});
export
default RelayApp;
For the child component, you set the eventId and onChange event handler as props from parent component. And in the parent componet you implement the event handler and call this.props.setVariables({eventId: someVal}) like
// Child Component
export default class Menu extends Component {
render() {
return(
<ul>
<li onClick={() => this.props.selectItem(val)}>{val}</li>
...
</ul>
)
}
}
// Parent Component
class Main extends Component {
_selectItem = (val) => {
this.props.relay.setVariables({eventId: val});
}
render() {
return(
<div>
<Menu selectItem={() => this._selectItem}/>
</div>
)
}
}
let RelayApp = ...
export default Main
Hope this will help.

There is no easy way to solve this. Either use react-router-relay or nest your query like this and use this.props.relay.setVariables()
viewer {
eventState(eventid:$eventid) {
data
}
}