Develop Reference

Parent scope not triggering child rerender in React

i have a prent comp and a child cmponent. as follows
parent
export class ExpressionMenu extends Component {
constructor(props) {
super(props)
}
state = {
apiArray: [],
}
updateStateFromChild = (arrayType, propertyType, value) => {
let { apiArray } = this.state
let currentArray = []
let idx = apiArray.findIndex((q) => q.id === id)
currentArray = apiArray
switch(propertyType) {
case 'updateObject': {
currentArray = value
break;
}
}
this.setState({
apiArray: currentArray
})
}
render () {
const {
apiArray
} = this.state
return (
<React.Fragment>
<div >
<div>
<ApiPanel
apiArray={apiArray}
updateStateFromChild={this.updateStateFromChild}
/>
</div>
</div>
</React.Fragment>
)
}
}
ExpressionMenu.propTypes = {
styleOverride: PropTypes.object,
eventHandler: PropTypes.func,
};
export default ExpressionMenu;
child
export class ApiPanel extends Component {
constructor(props) {
super(props),
}
removeApi = (id) => {
let { apiArray } = this.props
apiArray = apiArray.filter((q) => q.id !== id);
this.props.updateStateFromChild('api', 'updateObject', apiArray)
};
addApi = () => {
let { apiArray } = this.props
const id = uniqid();
let obj = {}
obj.id = id
apiArray.push(obj)
this.props.updateStateFromChild('api', 'updateObject', apiArray)
};
render() {
const { apiArray } = this.props
return (
<React.Fragment>
{
apiArray.map((apiObj, i) =>
<div key={i} >
<span onClick={() => this.removeApi(apiObj.id) } className={[classes.deleteRow,'material-icons'].join(' ')}>
close
</span>
<div>
<label><b>Hi</b></label>
</div>
<div onClick={this.addApi}>+Add Api</div>
}
</React.Fragment>
)
}
}
ApiPanel.propTypes = {
apiArray: PropTypes.array,
updateStateFromChild: PropTypes.func
}
export default ApiPanel
Now when i call addApi(), it updates the parent but doesnt rerenders the child.
But when i call removeApi() , it updates parent as well as rerenders the child component properly.
in the first case when i manually reload the componnt i can see the change.
Dont understand why this is happening

Try to change your addApi function.
addApi = () => {
let { apiArray } = this.props
this.props.updateStateFromChild('api', 'updateObject', [...apiArray, {id : uniqid()} ])
};
You need to return an enriched copy of your array

Whenever we are updating the stating using arrays, objects. We need to always create a new array [...array], a new object {...obj}. Because if we update value in the array or obj without creating it won't change the reference value hence it assumes the state is not update and won't re-render.

React.js : Updating State of Nested Object

Front End - Front End
Upon clicking the star, I want to update the state of nested object, with the new rating value of star.
I tried many things but it didnt work as states are immutable.
Nested State
Can some upon please suggest how can I update the value in nested object
onStarClicked = (kTypName, subItemId1, newRating) => {
//console.log(subItemId.split("_"));
let evaluation = subItemId1.split("_")[0];
let subItemId = subItemId1.split("_")[1];
console.log(subItemId);
const r = { ...this.state.ratings };
let kT = r.knowledgeTypes;
let sub = '', kTN = '', kIN = '';
kT.map(knowledgeType => {
//console.log(knowledgeType.knowledgeTypeId);
knowledgeType.knowledgeItems.map(knowledgeItem => {
//console.log(knowledgeItem.knowledgeItemId);
knowledgeItem.subItems.map(knowledgeSubItem => {
//console.log(knowledgeSubItem.subItemId);
if (subItemId === knowledgeSubItem.subItemId) {
kTN = knowledgeType.knowledgeTypeName;
kIN = knowledgeItem.knowledgeItemName;
sub = knowledgeSubItem;
if (evaluation === "self") {
sub.evaluation.self.rating = newRating;
}
else if (evaluation === "evaluator") {
sub.evaluation.evaluator.rating = newRating;
}
//alert(evaluation + subItemId + ' ' + newRating);
//return;
}
})
})
});
this.setState({
...this.state,
ratings: {
...this.state.ratings,
knowledgeTypes: [
...this.state.ratings.knowledgeTypes,
this.state.ratings.knowledgeTypes.filter(kt => kt.knowledgeTypeName !== kTN),
{
...this.state.ratings.knowledgeTypes.knowledgeItems.
filter(ki => ki.knowledgeItemName !== kIN),
knowledgeItems: {
...this.state.ratings.knowledgeTypes.knowledgeItems.subItems.
filter(si => si.subItemId !== subItemId),
sub
}
}]
}
});
}

You basically have to create a new empty array of knowledgeTypes and use the current state to find which item of the state you need to change using Object.keys/map/filter functions.
You'd use the current state in a variable and modify that variable only. You'd likely not mess with the actual state object in any way.
After you have done that, simply append it to the empty array. Then you can setState() the new array to the actual state property.
class MyComponent extends React.Component {
constructor(props) {
super(props);
this.state = {
financialYear: "2019-20",
quarter: "Q1",
isCurrentQuarter: true,
knowledgeTypes: [
{
knowledgeTypeName: "Technology",
knowledgeItems: [
{
knowledgeItemName: "Java",
subItems: [
{
subItemId: "2",
subItemName: "Collections",
evaluation: {
self: {
ntnet: "Joe",
rating: 1,
isEditable: true
}
}
}
]
}
]
}
]
};
}
handleClick = e => {
const { knowledgeTypes } = this.state;
// transformation
const itemToChange = knowledgeTypes.map(item => {
if (item.knowledgeTypeName === "Technology") {
return item;
}
});
const currItems = itemToChange[0].knowledgeItems[0].subItems;
const subItem = currItems.map(item => {
if (item.subItemId === "2") {
return item;
}
});
const person = subItem[0].evaluation;
person.self.rating = 55; //change
const newKnowledgeTypes = [];
knowledgeTypes.map(item => {
if (item.knowledgeTypeName === "Technology") {
newKnowledgeTypes.push(itemToChange);
}
newKnowledgeTypes.push(item);
});
this.setState({
knowledgeTypes: newKnowledgeTypes
});
console.log(this.state);
};
render() {
return (
<div>
MyComponent
<button onClick={this.handleClick}>Hello</button>
</div>
);
}
}
The sandbox can be found on https://codesandbox.io/s/musing-dew-8r2vk.
Note: It is advisable you do not use nested state objects because state objects are something more lightweight so that they do not have performance considerations.

import React, { Component } from 'react';
import Auxilary from '../../../hoc/Auxilary/auxilary';
import KnowledgeItems from '../KnowledgeItems/KnowledgeItems';
import Tabs from 'react-bootstrap/Tabs';
import Tab from 'react-bootstrap/Tab';
import knowledge from '../../../assests/staticdata.json';
import './QuarterLog.css';
class QuarterLog extends Component {
constructor() {
super();
this.state = {
"financialYear": "",
"quarter": "",
"isCurrentQuarter": "",
"knowledgeTypes": []
}
}
onStarClicked = (kTypName, kItemName, subItemIdName, newRating) => {
let evaluation = subItemIdName.split("_")[0];
let subItemId = subItemIdName.split("_")[1];
const { knowledgeTypes } = this.state;
// transformation
let knowledgeTypeToChange = knowledgeTypes.map(kType => {
if (kType.knowledgeTypeName === kTypName) {
return kType;
}
});
knowledgeTypeToChange = knowledgeTypeToChange.filter(function (element) {
return element !== undefined;
});
console.log(knowledgeTypeToChange[0]);
let knowledgeItemToChange = knowledgeTypeToChange[0].knowledgeItems.map(item => {
if (item.knowledgeItemName === kItemName) {
return item;
}
});
knowledgeItemToChange = knowledgeItemToChange.filter(function (element) {
return element !== undefined;
});
let knowledgeSubItem = knowledgeItemToChange[0].subItems.map(subItem => {
if (subItem.subItemId === subItemId) {
return subItem;
}
});
knowledgeSubItem = knowledgeSubItem.filter(function (element) {
return element !== undefined;
});
console.log(knowledgeSubItem);
let personEvaluations = knowledgeSubItem[0].evaluation;
if (evaluation === "self") {
personEvaluations.self.rating = newRating.toString(); //change
}
else if (evaluation === "evaluator") {
personEvaluations.evaluator.rating = newRating.toString(); //change
}
const newKnowledgeTypes = [];
knowledgeTypes.map(item => {
if (item.knowledgeTypeName === kTypName) {
newKnowledgeTypes.push(knowledgeTypeToChange[0]);
}
else
newKnowledgeTypes.push(item);
});
this.setState({
knowledgeTypes: newKnowledgeTypes
});
console.log(this.state);
}
componentDidMount() {
// TODO: remove staticdata.js and call REST API and set the response in state
this.setState({
...this.state,
"financialYear": knowledge.financialYear,
"quarter": knowledge.quarter,
"isCurrentQuarter": knowledge.isCurrentQuarter,
"knowledgeTypes": knowledge.knowledgeTypes
})
}
onSubmitRatings = () => {
console.log(this.state);
}
render() {
let data = knowledge; //remove this code, once REST API is implemented
const posts = this.state.knowledgeTypes.map(knowledgeType => {
return (
<Tab key={knowledgeType.knowledgeTypeName} eventKey={knowledgeType.knowledgeTypeName}
title={knowledgeType.knowledgeTypeName}>
<KnowledgeItems
kTypeName={knowledgeType.knowledgeTypeName}
kItems={knowledgeType.knowledgeItems}
ratings={this.state.ratings}
onstarclicked={this.onStarClicked}
/>
</Tab>)
});
return (
<Auxilary>
<div className="d-flex justify-content-between flex-wrap flex-md-nowrap align-items-center pt-3 pb-2 mb-3 border-bottom">
<div><h1>Financial Year : {data.financialYear}</h1></div>
<div><h2>Quarter : {data.quarter}</h2></div>
</div>
<div>
<Tabs defaultActiveKey="Domain" id="uncontrolled-tab-example">
{posts}
</Tabs>
</div>
<button onClick={this.onSubmitRatings}> Submit </button>
</Auxilary>
);
}
}
export default QuarterLog;

Component did update returning always the same props and state

I found a lot of solutions about this problem but none of them work.
I have a view which renders dynamically components depending on the backend response
/**
* Module dependencies
*/
const React = require('react');
const Head = require('react-declarative-head');
const MY_COMPONENTS = {
text: require('../components/fields/Description'),
initiatives: require('../components/fields/Dropdown'),
vuln: require('../components/fields/Dropdown'),
severities: require('../components/fields/Dropdown'),
};
const request = restclient({
timeout: 5000,
baseURL: '/api',
});
const { DropdownItem } = Dropdown;
class CreateView extends React.Component {
constructor(props) {
super(props);
this.state = {
modal: false,
states: props.states,
error: props.error,
spinner: true,
state: props.state,
prevState: '',
components: [],
};
this.handleChange = this.handleChange.bind(this);
this.getRequiredFields = this.getRequiredFields.bind(this);
this.onChangeHandler = this.onChangeHandler.bind(this);
this.changeState = this.changeState.bind(this);
this.loadComponents = this.loadComponents.bind(this);
}
componentDidMount() {
this.loadComponents();
}
onChangeHandler(event, value) {
this.setState((prevState) => {
prevState.prevState = prevState.state;
prevState.state = value;
prevState.spinner = true;
return prevState;
}, () => {
this.getRequiredFields();
});
}
getRequiredFields() {
request.get('/transitions/fields', {
params: {
to: this.state.state,
from: this.state.prevState,
},
})
.then((response) => {
const pComponents = this.state.components.map(c => Object.assign({}, c));
pComponents.forEach((c) => {
c.field.required = 0;
c.field.show = false;
});
response.data.forEach((r) => {
const ob = pComponents.find(c => c.field.name === r.name);
if (ob) {
ob.field.required = r.required;
ob.field.show = true;
}
});
this.setState({
components: pComponents,
fields: response.data,
spinner: false,
});
})
.catch(err => err);
}
loadComponents() {
this.setState((prevState) => {
prevState.components = Object.keys(MY_COMPONENTS).map((k) => {
const field = {
name: k,
required: 0,
show: true,
};
return {
field, component: MY_COMPONENTS[k],
};
});
return prevState;
});
}
handleChange(field, value) {
this.setState((prevState) => {
prevState[field] = value;
return prevState;
});
}
changeState(field, value) {
this.setState((prevState) => {
prevState[`${field}`] = value;
return prevState;
});
}
render() {
const Components = this.state.components;
return (
<Page name="CI" state={this.props} Components={Components}>
<Script src="vendor.js" />
<Card className="">
<div className="">
<div className="">
<Spinner
show={this.state.spinner}
/>
{Components.map((component, i) => {
const Comp = component.component;
return (<Comp
key={i}
value={this.state[component.field.name]}
field={component.field}
handleChange={this.handleChange}
modal={this.state.modal}
changeState={this.changeState}
/>);
})
}
</div>
</div>
</div>
</Card>
</Page>
);
}
}
module.exports = CreateView;
and the dropdown component
const React = require('react');
const request = restclient({
timeout: 5000,
baseURL: '/api',
});
const { DropdownItem } = Dropdown;
class DrpDwn extends React.Component {
constructor(props) {
super(props);
this.state = {
field: props.field,
values: [],
};
}
componentDidUpdate(prevProps, prevState, snapshot) {
console.log('state', this.state.field);
console.log('prevState', prevState.field);
console.log('prevProps', prevProps.field);
console.log('props', this.props.field);
}
render() {
const { show } = this.props.field;
return (show && (
<div className="">
<Dropdown
className=""
onChange={(e, v) => this.props.handleChange(this.props.field.name, v)}
label={this.state.field.name.replace(/^./,
str => str.toUpperCase())}
name={this.state.field.name}
type="form"
value={this.props.value}
width={100}
position
>
{this.state.values.map(value => (<DropdownItem
key={value.id}
value={value.name}
primary={value.name.replace(/^./, str => str.toUpperCase())}
/>))
}
</Dropdown>
</div>
));
}
module.exports = DrpDwn;
The code actually works, it hide or show the components correctly but the thing is that i can't do anything inside componentdidupdate because the prevProps prevState and props are always the same.
I think the problem is that I'm mutating always the same object, but I could not find the way to do it.
What I have to do there is to fill the dropdown item.
Ps: The "real" code works, i adapt it in order to post it here.

React state is supposed to be immutable. Since you're mutating state, you break the ability to tell whether the state has changed. In particular, i think this is the main spot causing your problem:
this.setState((prevState) => {
prevState.components = Object.keys(MY_COMPONENTS).map((k) => {
const field = {
name: k,
required: 0,
show: true,
}; return {
field, component: MY_COMPONENTS[k],
};
});
return prevState;
});
You mutate the previous states to changes its components property. Instead, create a new state:
this.setState(prevState => {
const components = Object.keys(MY_COMPONENTS).map((k) => {
const field = {
name: k,
required: 0,
show: true,
};
return {
field, component: MY_COMPONENTS[k],
};
});
return { components }
}
You have an additional place where you're mutating state. I don't know if it's causing your particular problem, but it's worth mentioning anyway:
const pComponents = [].concat(this.state.components);
// const pComponents = [...this.state.components];
pComponents.forEach((c) => {
c.field.required = 0;
c.field.show = false;
});
response.data.forEach((r) => {
const ob = pComponents.find(c => c.field.name === r.name);
if (ob) {
ob.field.required = r.required;
ob.field.show = true;
}
});
You do at make a copy of state.components, but this will only be a shallow copy. The array is a new array, but the objects inside the array are the old objects. So when you set ob.field.required, you are mutating the old state as well as the new.
If you want to change properties in the objects, you need to copy those objects at every level you're making a change. The spread syntax is usually the most succinct way to do this:
let pComponents = this.state.components.map(c => {
return {
...c,
field: {
...c.field,
required: 0,
show: false
}
}
});
response.data.forEach(r => {
const ob = pComponents.find(c => c.field.name === r.name);
if (ob) {
// Here it's ok to mutate, but only because i already did the copying in the code above
ob.field.required = r.required;
ob.field.show = true;
}
})

ArticlesGrid where are Article.props? or How to reference props?

In the ArticlesGrid example we have the following render function:
render () {
return this.state.articles && (
<div className='articles'>
{ this.state.articles.map( function (article) {
return <Article article={article} key={article.id} />;
})}
</div>
);
}
So we have a component Article which has as one of it's props article which equals the object article, so far so good
Could someone explain what's going on with the next statement:
var Article = function({article}) {
why isn't it
var Article = function(this.props.article) {
??
in fact, when I try to console.log this.props I get undefined. I thought Article was a component too.
UPDATE: Here's the entire code:
class ArticlesGrid extends React.Component {
constructor(props) {
super(props);
this.state = {
articles: []
};
}
componentDidMount () {
var url =
'http://api.nytimes.com/svc/search/v2/articlesearch.json?'
+ 'api-key=d68154fxxxxxxxxxxxxxxxxc7f5';
$.getJSON(url, function(data, status) {
return this.setState({articles: this.parse(data)});
}.bind(this));
}
parse(results) {
if(!results || !results.response) return [];
var articles = results.response.docs;
var parsedArticles = [];
for (var i = 0; i < articles.length;i++){
var article = articles[i];
if (article.multimedia.find(this.isXL)) {
parsedArticles.push({
id: article._id,
title: article.headline.main || 'Untitled',
imageURL: article.multimedia.find(this.isXL).url || '#',
webURL: article.web_url || '#'
});
}
}
return parsedArticles;
}
isXL (image) {
return image.subtype === 'xlarge';
}
render () {
return this.state.articles && (
<div className='articles'>
{ this.state.articles.map( function (article) {
return <Article article={article} key={article.id} />;
})}
</div>
);
}
}
var Article = function({article}) {
var imgURL = 'https://static01.nyt.com/' + article.imageURL;
return (
<div className='article'>
<a className='article-link' href={article.webURL}>
<img className='article-image'
title={article.title}
src={imgURL} />
</a>
</div>
);
}
ReactDOM.render(<ArticlesGrid/>,document.getElementById('container'));

when I try to console.log this.props I get undefined. I thought
Article was a component too.
Yes Article is a component too but it is a functional component. props to this are passed as argument to this function. So if you want to log props of this component then you can do it following way
var Article = function(props) {
console.log(props)
var imgURL = 'https://static01.nyt.com/' + article.imageURL;
What is var Article = function({article}) {
This is called object destructuring. It means that if an object is passed to this function then take article property of that object. So basically
var Article = function({article}) {
roughly means
var Article = function(props) {
var article = props.article
...

React remove element from onclick

When a user deletes an item from their cart, I have the item displayed with a button to add it back to the cart. This works. Once the user adds the item back to their cart, I want the item in the display component to be removed. Here is my code for reference.
CART:
class Cart extends Component {
constructor(props) {
super(props);
this.state = {differences: [],};
}
componentWillReceiveProps(nextProps){
let thisProps = this.props.cart.items;
let theNextProps = nextProps.cart.items;
if (thisProps.map(i => i.sku).some(item => !theNextProps.map(i => i.sku).includes(item))) {
let diff = [thisProps.filter(item => !theNextProps.includes(item))];
this.setState({differences: this.state.differences.concat(diff)});
}
}
...
render = () => {
<CartAddBack data={this.state.differences} onAddToCart={this.props.addToCart} />
<CheckoutSection className='Checkout-cart-items' titleKey='checkout.items.title'>
{this.props.cart.items.map((item) => {
return (
<CheckoutItem item={item} key={item.sku} onRemoveProduct={this.props.removeFromCart} onUpdateQuantity={this.props.updateCartItem}/>
);
})}
</CheckoutSection>
}
}
CartAddBack:
class CartAddBack extends Component {
constructor() {
super();
this.state = {deleted: null};
this.onDelete = this.onDelete.bind(this);
}
onDelete(id){
console.log("THE SKU SHOULD BE HERE", id);
this.setState(id);
}
render() {
let {data} = this.props;
let theData = data.map(i => parseInt(i[0].sku));
let theStated = this.state.deleted;
return (
<div>
{data &&
<div className="CartAddBack">
<div className="CartAddBack-Wrapper">
<ul className="CartAddBack-Item-ul">
{theStated != null
? theData.filter(i => !theStated.includes(i)) &&
<CartAddBackItem data={item[0]} onAddToCart={this.props.onAddToCart} onDelete={this.onDelete}/>
: data.map((item) => {
return <CartAddBackItem data={item[0]} onAddToCart={this.props.onAddToCart} onDelete={this.onDelete}/>
})
}
</ul>
</div>
</div>
}
</div>
)
}
}
CartAddBackItem:
class CartAddBackItem extends Component {
constructor() {
super();
this.onClick = this.onClick.bind(this);
}
onDelete(){
this.props.onDelete({deleted: this.props.data.sku})
}
allowSubmit() {
this.setState({
allowSubmit: true,
});
}
onClick() {
if (this.props.data) {
if (this.props.data.quantity <= this.props.data.inventory_quantity) {
const success = () => {
this.allowSubmit();
},
failure = (err) => {...};
this.props.onAddToCart({
...{sku: this.props.data.sku, quantity: this.props.data.quantity}, quantity: this.props.data.quantity}).then(success, failure);
}
else {
this.setState=({display: false});
const success = () => {
this.allowSubmit();
},
failure = (err) => {...};
this.props.onAddToCart({
...{sku: this.props.data.sku, quantity: this.props.data.quantity}, quantity: 1}).then(success, failure);
}
}
}
render() {
let {data} = this.props;
return (
<li className="CartAddBackItem">
{data &&
<div className="CartAddBackItem-Wrapper">
<Button className="CartAddBackItem-button" onClick={this.onClick}><FormattedMessage id="cart.cartAddBack"/></Button>
<Link to={`product/${data.sku}`} className="CartAddBackItem-Link">
<p className="CartAddBackItem-title">{data.title}</p>
</Link>
</div>
}
</li>
)
}
}
I want CartAddBack to remove CartAddBackItem if the item was clicked in CartAddBackItem. Only thing I havent tried that I just thought about was to make a componentWillReceiveProps inside CartAddBack. But there has to be a better way. Issue I'm running into is my mapping items into CartAddBackItem. The gross looking {theStated != Null ? theData.filter(i =>... allows me to add items to the cart. It works if it was only data.map((item)=>... but I want to show my thinking. Any advice?