Develop Reference

componentDidUpdate(prevProps, prevState, snapshot): prevProps is undefined

I am pretty new to React and I am trying to build this simple web app that takes a stock tag as an input and updates the graph based on the performance of the given stock. However, I can't get my graph to update. I tried using componentDidUpdate(prevProps, prevState, snapshot), but for some reason prevProps is undefined and I don't know/understand why. I tried searching online and reading the doc file, but I still can't figure it out. Any help would be appreciated.
import Search from './Search.js'
import Graph from './Graph.js'
import Sidebar from './Sidebar.js'
import './App.css'
import React, { Component } from 'react';
class App extends Component {
constructor(props) {
super(props);
this.state = {
data: [{
x: [],
close: [],
decreasing: { line: { color: '#FF0000' } },
high: [],
increasing: { line: { color: '#7CFC00' } },
line: { color: 'rgba(31,119,180,1)' },
low: [],
open: [],
type: 'candlestick',
xaxis: 'x',
yaxis: 'y'
}]
,
layout: {
width: 1500,
height: 700,
font: { color: '#fff' },
title: { text: 'Stock', xanchor: "left", x: 0 }, paper_bgcolor: '#243b55', plot_bgcolor: '#243b55', yaxis: { showgrid: true, color: '#fff' },
xaxis: {
zeroline: true, color: '#fff', showgrid: true, rangeslider: {
visible: false
}
}
},
searchfield: '',
stocktag: ' '
};
this.onSearchChange = this.onSearchChange.bind(this);
this.onSubmitSearch = this.onSubmitSearch.bind(this);
}
componentDidMount() {
document.body.style.backgroundColor = '#243b55';
this.loadGraphInfo();
}
componentDidUpdate(prevProps, prevState, snapshot){
console.log(prevProps.stocktag);
console.log(prevState.stocktag);
if (prevProps.stocktag !== prevState.stocktag) {
//this.fetchData('SPY');
}
}
onSearchChange = (event) => {
var search = event.target.value;
this.setState({ stocktag: search });
}
onSubmitSearch = (e) => {
var search = this.state.searchfield;
this.setState({ stocktag: search });
}
fetchData(stock) {
//GET DATA
//UPDATE STATE
}
loadGraphInfo() {
if (this.state.stocktag == ' ') {
this.fetchData('SPY');
} else {
this.fetchData(this.state.stocktag);
}
}
render() {
return (
<div className="App" >
<Sidebar />
<Search searchChange={this.onSearchChange} submitChange={this.onSubmitSearch} />
<Graph data={this.state.data} layout={this.state.layout} />
</div>
);
}
}
export default App;
import React, { Component } from 'react';
import './Search.css'
const Search = ({ searchChange, submitChange }) => {
return (
<div>
<div class="SearchCompInput">
<input class="SearchBar" type="text" onChange={searchChange}/>
</div>
<div class="SearchCompButton">
<button class="SearchButton" onClick={submitChange}>Search</button>
</div>
</div>
);
}
export default Search;

The prevProps.stocktag is undefined because you didn't pass any props to App component. Try this in your index.js you will see preProps value but actually it does not make any sense.
render(<App stocktag='' />, document.getElementById('root'));
componentDidUpdate(prevProps, prevState, snapshot){
console.log(prevProps.stocktag);
console.log(prevState.stocktag);
if (prevProps.stocktag !== prevState.stocktag) {
//this.fetchData('SPY');
}
}

I am not quite sure on what you are trying to accomplish here but the first thing I notice is you setState of stocktag to this.state.searchfield which is ' ' in your onSubmitSearch function.
onSearchChange = (event) => {
var search = event.target.value;
this.setState({ stocktag: search });
}
onSubmitSearch = (e) => {
var search = this.state.searchfield;
this.setState({ stocktag: search });
}
Add I will also like to add that it is good practice to set value of input to a state value like so
import React, { Component, useState } from 'react';
import './Search.css'
const Search = ({ searchChange, submitChange }) => {
const [inputValue, setInputValue] = useState('')
const handleChange = (e) => {
setInputValue(e.target.value)
searchChange(e)
}
return (
<div>
<div class="SearchCompInput">
<input class="SearchBar" type="text" value = {inputValue} onChange={handleChange}/>
</div>
<div class="SearchCompButton">
<button class="SearchButton" onClick={submitChange}>Search</button>
</div>
</div>
);
}
export default Search;

I had this problem, and it was because there was a child class that was calling super.componentDidUpdate() WITHOUT passing in the parameters. So the child class looked something like:
componentDidUpdate() {
super.componentDidUpdate();
... <-- other stuff
}
And I had to change it to:
componentDidUpdate(prevProps, prevState) {
super.componentDidUpdate(prevProps, prevState);
... <-- other stuff
}

There is an error on the return ( and I cannot understand why

import { connect } from 'react-redux'
import { Link } from 'react-router-dom'
class MyStories extends React.Component {
addFavorite = (e) => {
this.setState({
bgcolor: "blue"
})
}
render () {
const { stories } = this.props;
const { storyBriefs } = this.props.stories.length > 0 ?
stories.map(t => (<div className="menu-inner-container"><p key={t.id}><Link to={`/stories/${t.id}`}>{t.attributes.title}</Link>
<div className="addFavoriteCss"
style={{backgroundColor: this.state.bgColor}}
onClick={this.addFavorite}> Favorite</div>
</p></div>))
//refactor - create a button that will allow for us to mark which our favorites are
return (
{ this.props.storyBriefs }
);
}
}
const mapStateToProps = state => {
return {
stories: state.myStories
}
}
export default connect(mapStateToProps)(MyStories)
getting this error
./src/components/MyStories.js
Line 26: Parsing error: Unexpected token, expected ":"
return (
^
{ this.props.storyBriefs }
);
}
I converted a functional component to a class component so that I could manipulate the state in order to change the color of the favorite button -- (I cannot use hooks or redux for the button function) Can anyone tell me what I am doing wrong?

You need to complete the ternary operator by adding :
const storyBriefs = this.props.stories.length > 0 ?
stories.map(t => (<div className="menu-inner-container"><p key={t.id}><Link to={`/stories/${t.id}`}>{t.attributes.title}</Link>
<div className="addFavoriteCss"
style={{backgroundColor: this.state.bgColor}}
onClick={this.addFavorite}> Favorite</div>
</p></div>))
: [] // you need something here after the ':', an empty array could be useful in this case
return storyBriefs
or you could shorten it to
return stories.map(t => (<div className="menu-inner-container"><p key={t.id}><Link to={`/stories/${t.id}`}>{t.attributes.title}</Link>
<div className="addFavoriteCss"
style={{backgroundColor: this.state.bgColor}}
onClick={this.addFavorite}> Favorite</div>
</p></div>))

As Jaromanda X said { this.props.storyBriefs } isn't valid. you need to provide the key value pair unless the variable doesn't have dot notation then you can define the object like that

This was the final code and it works,
import React from "react"
import { connect } from "react-redux"
import { Link } from "react-router-dom"
class MyStories extends React.Component {
constructor(props) {
super(props);
this.state = {
button: false
};
this.addFavorite = this.addFavorite.bind(this);
}
addFavorite = id => {
this.setState({
button: id
});
};
render() {
return this.props.stories.map(t => (
<div className="menu-inner-container">
<p key={t.id}>
<Link to={`/stories/${t.id}`}>{t.attributes.title}</Link>
<button
key={t.id}
className={this.state.button===t.id ? "buttonTrue" : "buttonFalse"}
onClick={() => this.addFavorite(t.id)}
>
Favorites
</button>
</p>
</div>
));
}
}
//refactor - create a button that will allow for us to mark which our favorites are
const mapStateToProps = state => {
return {
stories: state.myStories
};
};
export default connect(mapStateToProps)(MyStories);

Updating state on first render only?

Using react-native, I'm creating sub-Components within the parent App and providing their position to the array this.state.objLocation within the parent App.
I can get the initial location data into the array straight after the render, but because my subcomponents are draggable, each time they re-render on drag, it adds a new position object to the array.
I'd like to avoid this, and I thought that creating this.state = { firstRender: true } in the constructor and then using componentDidMount = () => { this.setState({ firstRender: false }) } after the first render would allow me to create a 'gate' to stop the addition of the extra position objects.
I can see that if I comment out //componentDidMount = () => { this.setState({ firstRender: false }) } then I will get multiple entries to my array but if it's included in the class I get absolutely none.
So possibly my interpretation of the render lifecycle and componentDidMount is incorrect?
Here is my code.
// App
import React, { Component } from 'react';
import { View, Text, } from 'react-native';
import styles from './cust/styles';
import Draggable from './cust/draggable';
const dataArray = [{num: 1,id: 'A',},{num: 2,id: 'B',},{num: 3,id: 'Z',}]
export default class Viewport extends Component {
constructor(props){
super(props);
this.state = {
dID : null,
objLocation: [],
firstRender: true,
};
}
render(){
return (
<View style={styles.mainContainer}>
<View style={styles.draggableContainer}>
<Text>Draggable Container</Text> {dataArray.map( d => { return(
<Draggable
id={d.id}
onLayout={ e=> this.onLayout(e)}
onPanResponderGrant={(dID) =>this.setState({ dID })}
onPanResponderRelease={() => this.setState({dID: null})} /> ) })}
<View style={[styles.findPoint ]} />
</View>
<View style={styles.infoBar}>
<Text>{this.state.dID ? this.state.dID : ''}</Text>{this.compFrame()}
</View>
</View>
);
}
onLayout = (e) => {
if ( e && this.state.firstRender) {
const n = e.nativeEvent.layout;
const position = {
width: n.width,
height: n.height,
x: n.x,
y: n.y
}
console.log(position);
this.setState({
objLocation: this.state.objLocation.concat([position])
});
}
}
componentWillMount = () => {
console.log("START");
}
compFrame = () => {
return(
this.state.objLocation.map( d => {<View style={[styles.findPoint2,{left: d.x, top: d.y, width: d.width, height: d.height} ]} ></View>})
)
}
componentDidMount = () => {
this.setState({firstRender: true })
console.log(this.state.objLocation.length);
}
}
// Draggable
import React, { Component } from 'react';
import { Text, PanResponder, Animated } from 'react-native';
import styles from './styles';
class Draggable extends Component {
constructor(props) {
super(props);
this.state = {
pan: new Animated.ValueXY(),
};
this.panResponder = PanResponder.create({
onStartShouldSetPanResponder: () => true,
onPanResponderGrant: () => {
this.props.onPanResponderGrant(this.props.id);
},
onPanResponderMove: Animated.event([ null, {
dx: this.state.pan.x,
dy: this.state.pan.y,
},
]),
onPanResponderRelease: () => {
Animated.spring(this.state.pan, { toValue: { x: 0, y: 0 } }).start();
this.props.onPanResponderRelease();
},
});
}
render() {
return (
<Animated.View
onLayout={ (e) => this.props.onLayout(e) }
{...this.panResponder.panHandlers}
style={[this.state.pan.getLayout(), styles.circleAlt, styles.position]}>
<Text style={styles.textAlt}>Drag me!</Text>
<Text style={styles.textNum}>{this.props.id}</Text>
</Animated.View>
);
}
componentDidMount = () => {
this.props.onLayout(this.props.dragEvent)
}
}
export default Draggable;
// Output of console.log
START xxx
0
{width:108,height:108,x:133.5,y:376.5}
{width:108,height:108,x:133.5,y:78.5}
{width:108,height:108,x:133.5,y:227.5}

You could set the firstRender state in onLayout function
onLayout = (e) => {
if ( e && this.state.firstRender) {
const n = e.nativeEvent.layout;
const position = {
width: n.width,
height: n.height,
x: n.x,
y: n.y
}
console.log(position);
this.setState({
firstRender: false,
objLocation: this.state.objLocation.concat([position])
});
}
}

According to the information provided by you, your onLayout function is called by the component so its not included in the component lifecycle process, so when the component completes its lifecycle it goes into componentDidMount after mounting (which is not calling onLayout func) & thus changed the firstRender state to false and hence when you drag the component each time it goes from true to false.
I hope this explains

I feel like I've hacked this, to get it to work, so please correct me as to correct procedure.
This is the onLayout method from the App. I've included an if statement that checks if the new positions array length is equal too the dataArray length that the draggable items are based on.
It looks like this.
onLayout = (e) => {
if ( this.state.objLocation.length != dataArray.length ) {
if ( e ) {
const n = e.nativeEvent.layout;
const position = {
width: n.width,
height: n.height,
x: n.x,
y: n.y
}
console.log(position);
this.setState({
objLocation: this.state.objLocation.concat([position])
});
}
}
}

react-native-sketch module and component not working at all

import React, { Component } from 'react';
import {
AppRegistry,
Button,
StyleSheet,
View,
requireNativeComponent,
} from 'react-native';
import Sketch from 'react-native-sketch';
const styles = StyleSheet.create({
container: {
flex: 1,
},
sketch: {
height: 250, // Height needed; Default: 200px
},
});
export default class paintChalledgeNative extends Component {
constructor(props) {
super(props);
this.clear = this.clear.bind(this);
this.onReset = this.onReset.bind(this);
this.onSave = this.onSave.bind(this);
this.onUpdate = this.onUpdate.bind(this);
this.state = {
drawing: null,
};
}
onReset() {
console.log('bye bye drawing');
}
onSave() {
this.sketch.saveImage(this.state.drawing)
.then(data => console.log(data))
.catch(error => console.log(error));
}
onUpdate(base64Image) {
this.setState({ drawing: base64Image });
}
clear() {
this.sketch.clear();
}
render() {
return (
<View style={styles.container}>
<Sketch
fillColor="transparent"
strokeColor="#111111"
strokeThickness={2}
imageType="png"
onReset={this.onReset}
onUpdate={this.onUpdate}
ref={(sketch) => { this.sketch = sketch; }}
style={styles.sketch}
/>
<Button
onPress={this.clear}
title="clear drawing"
/>
<Button
disabled={!this.state.encodedSignature}
onPress={this.onSave}
title="Save drawing"
/>
</View>
);
}
}
AppRegistry.registerComponent('paintChalledgeNative', () => paintChalledgeNative);
building sketch app using 'react-native-sketch' the simulator is running but the sketch feature is not woking at all and the clear button crashes the app with and error in the image , the console is logging 20 similar error msgs to the one below
'In file included from /Users/waltershub/Desktop/paintChalledgeNative/node_modules/react-native-sketch/RNSketch/RNSketch.m:11:
../react-native/React/Base/RCTEventDispatcher.h:18:3: error: redefinition of enumerator 'RCTTextEventTypeChange'
RCTTextEventTypeChange,'

I think it's because you've used the 0.5 version of react-native-sketch, which wasn't compatible with React Native > 0.40. Since then, a new 1.0 version has been published, so maybe you could try again with this one?
(Disclaimer: I'm the maintainer of react-native-sketch)

MUI - How to animate Card depth on hover?

I want to animate the depth of the whole Card when the mouse is over it.
I try this (so-so I'm new in React) but I have no idea how to do it:
<Card
linkButton={true}
href="/servicios/"
onClick={Link.handleClick} zDepth={3}
onMouseEnter={this.setState({zDepth={1}})}>
</Card>
Thanks in advance.

5 years later and there is still no correct answer, you do not have to set the component state when it hovers, just use the pseudo-class :hover:
<Card
sx={{
':hover': {
boxShadow: 20, // theme.shadows[20]
},
}}
>
If you want to use styled():
const options = {
shouldForwardProp: (prop) => prop !== 'hoverShadow',
};
const StyledCard = styled(
Card,
options,
)(({ theme, hoverShadow = 1 }) => ({
':hover': {
boxShadow: theme.shadows[hoverShadow],
},
}));
<StyledCard hoverShadow={10}>
<Content />
</StyledCard>
Live Demo

constructor(props) {
super(props);
this.state = { shadow: 1 }
}
onMouseOver = () => this.setState({ shadow: 3 });
onMouseOut = () => this.setState({ shadow: 1 });
<Card
onMouseOver={this.onMouseOver}
onMouseOut={this.onMouseOut}
zDepth={this.state.shadow}
>
Updated #1
Full example
// StyledCard.js
import React, { Component } from 'react';
import { Card } from 'material-ui/Card';
class StyledCard extends Component {
state: {
shadow: 1
}
onMouseOver = () => this.setState({ shadow: 3 });
onMouseOut = () => this.setState({ shadow: 1 });
render() {
return (
<Card
onMouseOver={this.onMouseOver}
onMouseOut={this.onMouseOut}
zDepth={this.state.shadow}
>
{this.props.children}
</Card>
);
}
export default StyledCard;
.
// Container.js
import React from 'react';
import StyledCard from './StyledCard';
const Container = () => [
<StyledCard>Card 1</StyledCard>,
<StyledCard>Card 2</StyledCard>,
<StyledCard>Card 3</StyledCard>,
];
export default Container;
UPDATED #2
With HOC
// withShadow.js
import React from 'react';
const withShadow = (Component, { init = 1, hovered = 3 }) => {
return class extends React.Component {
state: {
shadow: init
};
onMouseOver = () => this.setState({ shadow: hovered });
onMouseOut = () => this.setState({ shadow: init });
render() {
return (
<Component
onMouseOver={this.onMouseOver}
onMouseOut={this.onMouseOut}
zDepth={this.state.shadow}
{...this.props}
/>
);
}
};
};
export default withShadow;
.
// Container.js
import React from 'react';
import { Card } from 'material-ui/Card';
import withShadow from './withShadow';
const CardWithShadow = withShadow(Card, { init: 2, hovered: 4 });
const Container = () => [
<CardWithShadow>Card 1</CardWithShadow>,
<CardWithShadow>Card 2</CardWithShadow>,
<CardWithShadow>Card 3</CardWithShadow>,
];
export default Container;

#Alex Sandiiarov answer didnt work for me. The docs show to use the raised property.
https://material-ui.com/api/card/
class Component extends React.Component{
state = {
raised:false
}
toggleRaised = () => this.setState({raised:!this.state.raised});
render(){
return <Card onMouseOver={this.toggleRaised}
onMouseOut={this.toggleRaised}
raised={this.state.raised}>
...
</Card>
}
}