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Reactjs closure when passing state to component

I got a react functional component:
const DataGrid = (props) =>
{
const [containerName, setContainerName] = useState("");
const [frameworkComponents, setFrameworkComponents] = useState(
{customLoadingOverlay: LoadingOverlayTemplate,
customNoRowsOverlay: UxDataGridCustomNoRows,
editButton: params => <ViewAndDeleteSetting {...params}
openAddConfigurationsWindow={openAddConfigurationsWindow}
onDeleteSetting={onDeleteSetting}/>,
});
useEffect(async () =>
{
if(props.containerName && props.containerName !== "")
{
setContainerName(props.containerName);
}
},[props.containerName]);
.
.
.
const onDeleteSetting = async (settingKey) =>
{
console.log("ON DELETE AND CONTAINER NAME:");
console.log(containerName); //HERE THE CONTAINER NAME IS EMPTY
...
}
return (
<UxDataGrid
frameworkComponents={frameworkComponents}/>
);
The container name inside useEffect exists and is not empty. As you can see in the comment in onDeleteSetting, the containerName is empty when this callback is invoked. I tried adding this to the useEffect after setContainerName:
setFrameworkComponents({customLoadingOverlay: LoadingOverlayTemplate,
customNoRowsOverlay: UxDataGridCustomNoRows,
editButton: params => <ViewAndDeleteSetting {...params}
openAddConfigurationsWindow={openAddConfigurationsWindow}
onDeleteSetting={onDeleteSetting}/>,
});
That didn't work.
How can I get the name inside the callback? There is no special need to leave that frameworkComponents struct in the state.. it can also be moved to somewhere else if you think its better

Try this in your useEffect, update the onDeleteSetting function with the new containerName when it's updated
.....
useEffect(async() => {
if (props.containerName && props.containerName !== "") {
setContainerName(props.containerName);
// move this function here
const onDeleteSetting = async(settingKey) => {
console.log("ON DELETE AND CONTAINER NAME:");
// use props.containerName since the state update is async
console.log(props.containerName);
...
}
// update your components with the updated functions
setFrameworkComponents(prevComponents => ({
...prevComponents,
editButton: params =>
<ViewAndDeleteSetting
{...params}
openAddConfigurationsWindow={openAddConfigurationsWindow}
onDeleteSetting={onDeleteSetting}
/>,
}));
}
}, [props.containerName]);
.....
This should provide the updated state with the updated function, if it works, I can add more details.

You almost certainly shouldn't be storing it in state. Props are essentially state controlled by the parent. Just use it from props. Copying props to state is usually not best practice.
If you're looking at one of the very rare situations where it makes sense to set derived state based on props, this page in the documentation tells you how to do that with hooks. Basically, you don't use useEffect, you do your state update right away.
Here's a full quote from the linked documentation:
How do I implement getDerivedStateFromProps?
While you probably don’t need it, in rare cases that you do (such as implementing a <Transition> component), you can update the state right during rendering. React will re-run the component with updated state immediately after exiting the first render so it wouldn’t be expensive.
Here, we store the previous value of the row prop in a state variable so that we can compare:
function ScrollView({row}) {
const [isScrollingDown, setIsScrollingDown] = useState(false);
const [prevRow, setPrevRow] = useState(null);
if (row !== prevRow) {
// Row changed since last render. Update isScrollingDown.
setIsScrollingDown(prevRow !== null && row > prevRow);
setPrevRow(row);
}
return `Scrolling down: ${isScrollingDown}`;
}
This might look strange at first, but an update during rendering is exactly what getDerivedStateFromProps has always been like conceptually.
If you did it the same way they did in that example, your component would still render with containerName set to the default state (""), it's just that it will then almost immediately re-render with the updated containerName. That makes sense for their example of a transition, but you could avoid that by making the prop's initial value the state's initial value, like this:
const DataGrid = (props) => {
const [containerName, setContainerName] = useState(props.containerName); // *** ONLY USES THE INITIAL PROP VALUE
const [frameworkComponents, setFrameworkComponents] = useState(
// ...
});
// *** Updates the state value (on the next render) if the prop changes
if (containerName !== props.containerName) {
setContainerName(props.containerName);
}
// ...
};
Every time the containerName prop changes, though, your component will render twice, which brings us back full circle to: Don't store it in state, just use it from props. :-)
Stepping back and looking at the component as a whole, I don't think you need any state information at all, but if your goal is to avoid having the frameworkComponents you pass UxDataGrid change unnecessarily, you probably want useMemo or React.memo rather than state.
For instance, with useMemo (but keep reading):
const DataGrid = ({containerName}) => {
const frameworkComponents = useMemo(() => {
const onDeleteSetting = async (settingKey) => {
console.log("ON DELETE AND CONTAINER NAME:");
console.log(containerName);
// ...
};
return {
customLoadingOverlay: LoadingOverlayTemplate,
editButton: params => <ViewAndDeleteSetting {...params}
openAddConfigurationsWindow={openAddConfigurationsWindow}
onDeleteSetting={onDeleteSetting} />,
};
}, [containerName]);
return (
<UxDataGrid frameworkComponents={frameworkComponents} />
);
};
But if componentName is your only prop, it may well be even simpler with React.memo:
const DataGrid = React.memo(({containerName}) => {
const onDeleteSetting = async (settingKey) => {
console.log("ON DELETE AND CONTAINER NAME:");
console.log(containerName);
// ...
};
return (
<UxDataGrid frameworkComponents={{
customLoadingOverlay: LoadingOverlayTemplate,
editButton: params => <ViewAndDeleteSetting {...params}
openAddConfigurationsWindow={openAddConfigurationsWindow}
onDeleteSetting={onDeleteSetting} />,
}} />
);
});
React.memo memoizes your component, so that your component function is only ever called again when the props change. Since everything in the component needs to update based on the componentName prop changing, that looks like a good match (but I don't know what UxDataGrid is).

The problem was with how I tried passing props to ViewAndDeleteSetting. If you want to pass prop to a cell rendered component, you shouldn't be doing it in frameworkComponents, but rather you need to do it in the column definition like this:
useEffect(() =>
{
let columns = [{headerName: '', cellRenderer: 'editButton', width: 90, editable: false,
cellRendererParams: {
openAddConfigurationsWindow: openAddConfigurationsWindow,
onDeleteSetting: onDeleteSetting
}},
.. other columns
]
setColumnDefinition(columns);
},[props.containerName]);
The columns with the cellRendererParams do gets recreated in the useEffect when the name changes, and then the component can access this params regularly via its props

Component not rerendering on state change?

Whenever setState() is called, the component doesn't seem to rerender. As you can see by my comments, the state does in fact change and render seems to be called again, but if I don't add that if statement and simply add a paragraph tag that displays the data it will give me an error. I'm sure I'm missing something simple, but any help is appreciated.
import React from "react";
import axios from "axios";
import { constants } from "../constants/constants";
const { baseURL, apiKey, userName } = constants;
class User extends React.Component {
constructor(props) {
super(props);
this.state = {
user: []
};
}
componentDidMount() {
let getUserInfo = axios.create({
baseURL,
url: `?
method=user.getinfo&user=${userName}&api_key=${apiKey}&format=json`
});
getUserInfo().then(response => {
let data = response.data;
console.log(data.user.playcount); //logs second, displays correct
this.setState(state => ({
user: data
}));
});
}
render() {
console.log(this.state); //logs first and third, doesn't work on first but does on third
let toReturn;
if (this.state.user.length > 0) {
toReturn = <p>{this.state.user.user.playcount}</p>;
} else {
toReturn = <p>didn't work</p>;
}
return <div>{toReturn}</div>;
}
}
export default User;

React LifeCycle function sequence is Constructor and then it calls render method.
In constructor method it initialises the state which is currently empty user array.
Now it calls render() method as this.state.user is an empty array, referencing something out of it gives an error
this.state.user.user.playcount
this will generate an error if you dont have if condition.
After the first render it will call componentDidMount, now you fetch something update state. As setState occurred, render will be called again Now you have something in this.state.user then displaying will happen.
this.state.user.length > 0 is true
Look at this: https://reactjs.org/docs/react-component.html and https://reactjs.org/docs/conditional-rendering.html
You can right in single tag using conditional render like this
<p>{this.state.user.length ? this.state.user.user.playcount : 'loading'}
Hope this helps.

I think your problem might have something to do with the changing shape of the user value. You initialise the value to an empty array, but then—after the fetch is done—you assume it's an object (by using user.user).
Maybe you could simplify the code a bit to look more like the one below?
/* imports */
class User extends React.Component {
constructor(props) {
super(props);
this.state = {
user: null // Make it explicit there's no value at the beginning.
};
}
componentDidMount() {
let getUserInfo = axios.create(/* ... */);
getUserInfo().then(response => {
let data = response.data;
this.setState({ // No need to for a setter function as you dno't rely on the previous state's value.
user: data.user // Assign the user object as the new value.
});
});
}
render() {
let toReturn;
// Since it's now a `null`, you can use a simple existence check.
if (this.state.user) {
// User is now an object, so you can safely refer to its properties.
toReturn = <p>{this.state.user.playcount}</p>;
} else {
toReturn = <p>No data yet.</p>;
}
return <div>{toReturn}</div>;
}
}
export default User;

ReactJS element not updating after setState being called

Good Afternoon,
I have a React component that is dynamically rendered in reponse to an API call. I have set the value of one of the elements to a state within the component. During an onClick function (minusOne) this value is supposed to change.
The value is initially rendered successfully based on the state, the function does indeed change the state, however the rendered element stays the same despite the state changing. Does anyone have any ideas of why this might be the case?
If you have any questions, please ask away!
export class Cart extends React.Component {
constructor(props) {
super(props);
this.state={
quantities: []
};
this.minusOne = this.minusOne.bind(this);
}
minusOne(i) {
var self = this;
return function() {
let quantities = self.state.quantities;
if (quantities[i] > 1) {
quantities[i] --;
}
self.setState({
quantities
})
}
}
componentDidMount() {
let cart = this.props.cartTotals;
this.setState({
cart
});
if(cart.lines) {
let cartTotal = [];
let quantities = [];
for (var i = 0; i < cart.lines.length; i++) {
if(cart.lines[i]) {
quantities.push(cart.lines[i].quantity);
}
}
//Initial setting of state
this.setState({
quantities
})
Promise.all(
cart.lines.map(
(cart, i) => axios.get('http://removed.net/article/' + cart.sku)
)
).then(res => {
const allCartItems = res.map((res, i) => {
const data = res.data;
return(
<div key={i} className="cart-item-container">
<img className ="cart-item-picture" src={data.image} name={data.name} />
<div className="cart-item-description">
<p>{data.name}</p>
<p>{data.price.amount} {data.price.currency}</p>
</div>
<div className="cart-item-quantity">
<button onClick={this.minusOne(i)} name="minus">-</button>
//This is the troublesome element
<p className="cart-current-quantity">{this.state.quantities[i]}</p>
<button name="plus">+</button>
</div>
</div>
)
})
this.setState({
allCartItems
})
})
}
}
render() {
return (
{this.state.allCartItems}
);
}
}
Thanks for reading! Any advice will be helpful.

There are two issues:
First, you need to render (including where the onClick is) in render(). ConponentDidMount is only called once and supposed to perform initialization but not render.
Then, there is a problem in minusOne:
quantities points to this.state.quantities. So you are changing the old state, React looks at both the old state and the new one, sees there is no change, and dodesn't render, although the values have changed.
If you will copy this.state.quantities to a new array, like:
newQ = this.state.quantities.slice(0, -1);
Then modify newQ, then do
this.setState({ quantities: newQ });
It should work.

I think you don't need to return a function at minusOne(i) method. Just update the state is enough. You should change the array by specific id.
let quantities = self.state.quantities;
let mutatedQuantities = quantities.map((el, index) => {
return (index === i) ? el - 1 : el;
})
this.setState({quantities: [...mutatedQuantities]})

--- edited ---
I deleted everything I wrote before to make it more concise.
Your problem is that you assign what you want to render to a variable in componentDidMount. This function does only get called once, hence you asigne the variable allCartItems only once. The setState function does not have any effect because it does not trigger componentDidMount and therefore your variable allCartItems does not get reassigned.
What can you do? Well you can do a lot of stuff to enhance your code. First I will let you know about how you can solve your problem and then give you some further improvements
To solve the problem of your component not updating when you call setState you should move your jsx to the render Method. In the componentDidMount you just get all the data you need to render your component and once you have it you can set a flag for example like ready to true. Below you can see an example of how your code could look like.
import React from 'react';
class Cart extends React.Component {
constructor(props) {
super(props);
this.state = {
carts: null,
ready: false,
};
}
componentDidMount() {
fetch('www.google.com').then((carts) => {
this.setState({
carts,
ready: true,
});
});
}
render() {
const myCarts = <h2> Count {this.state.carts} </h2>;
return (
{
this.state.ready
? myCarts
: <h2> Loading... </h2>
}
);
}
}
I made you a demo with a simple counter with some explanations of your case and how you can make it work. You can check it out codesandbox. In the NotWorkingCounter you can see the same problem as in your component of the variable not being updated. In the WorkingCount you can see an example where I implemented what a I wrote above with waiting until your data has arrived and only then render it.
Some more suggestions concerning code:
Those two syntaxes below are identical. One is just a lot more concise.
class Cart extends React.Component {
constructor(props) {
super(props);
this.state = {
carts: null,
ready: false,
};
}
}
class Cart extends React.Component {
state = {
carts: null,
ready: false,
}
}
I would suggest to use arrow function if you want to bind your context. Below you can see your example simplified and an example on how you can achieve the same thing with less syntax.
export class Cart extends React.Component {
constructor(props) {
super(props);
this.minusOne = this.minusOne.bind(this);
}
minusOne(i) {
///
}
}
export class Cart extends React.Component {
constructor(props) {
super(props);
}
minusOne = (i) => {
/// minus one function
}
}
Your minusOne could also be rewritten if you use arrow functions and be a lot smaller, something in the area of
minusOne = (i) => (i) => {
let quant = self.state.quantities[i];
if(quant > 1) {
this.setState({
quantities: quant-1,
})
}
}
In your componentDidMount you call this.setState twice. Every time you call this function your component gets rerender. So what happens in your component is when your mount your component it gets rendered the first time, once it is mounted componentDidMount gets called, in there you call this.setState again twice. This means your component get's rendered in the best case three times before the user sees your component. If you get multiple promises back this means your rerender your state even more. This can create a lot of load for your component to cope with. If you rerender every component three times or more you end up having some performance issues once your application grows. Try to not call setState in your componentDidUpdate more than once.
In your case your first call to setState is totally unnecessary and just creates load. You still have access to quantities in your promise. Just call setState once at the end of your promise.then() with both elements.
In the example below you are using the index i as a key. This is not a good case practice and react should also log you at least a warning in the console. You need to use a unique identifier which is not the index. If you use the index you can get sideeffects and weird rendering which is difficult to debut. Read more on it here
then(res => {
const allCartItems = res.map((res, i) => {
const data = res.data;
return(
<div key={i} className="cart-item-container">
Another suggestion is to replace all var with const or let, as var exposes your variable to the global scope. If you don't understand what that means read this.
Last but not least have a look at object deconstruction. It can help you to clean up your code and make it more resistant to unwanted sideffects.

How to make an API call on props change?

I'm creating a hackernews-clone using this API
This is my component structure
-main
|--menubar
|--articles
|--searchbar
Below is the code block which I use to fetch the data from external API.
componentWillReceiveProps({search}){
console.log(search);
}
componentDidMount() {
this.fetchdata('story');
}
fetchdata(type = '', search_tag = ''){
var url = 'https://hn.algolia.com/api/v1/search?tags=';
fetch(`${url}${type}&query=${search_tag}`)
.then(res => res.json())
.then(data => {
this.props.getData(data.hits);
});
}
I'm making the API call in componentDidMount() lifecycle method(as it should be) and getting the data correctly on startup.
But here I need to pass a search value through searchbar component to menubar component to do a custom search. As I'm using only react (not using redux atm) I'm passing it as a prop to the menubar component.
As the mentioned codeblock if I search react and passed it through props, it logs react once (as I'm calling it on componentWillReceiveProps()). But if I run fetchData method inside componentWillReceiveProps with search parameter I receive it goes an infinite loop. And it goes an infinite loop even before I pass the search value as a prop.
So here, how can I call fetchdata() method with updating props ?
I've already read this stackoverflow answers but making an API call in componentWillReceiveProps doesn't work.
So where should I call the fetchdata() in my case ? Is this because of asynchronous ?
Update : codepen for the project

You can do it by
componentWillReceiveProps({search}){
if (search !== this.props.search) {
this.fetchdata(search);
}
}
but I think the right way would be to do it in componentDidUpdate as react docs say
This is also a good place to do network requests as long as you compare the current props to previous props (e.g. a network request may not be necessary if the props have not changed).
componentDidMount() {
this.fetchdata('story');
}
componentDidUpdate(prevProps) {
if (this.props.search !== prevProps.search) {
this.fetchdata(this.props.search);
}
}

Why not just do this by composition and handle the data fetching in the main HoC (higher order component).
For example:
class SearchBar extends React.Component {
handleInput(event) {
const searchValue = event.target.value;
this.props.onChange(searchValue);
}
render() {
return <input type="text" onChange={this.handleInput} />;
}
}
class Main extends React.Component {
constructor() {
this.state = {
hits: []
};
}
componentDidMount() {
this.fetchdata('story');
}
fetchdata(type = '', search_tag = '') {
var url = 'https://hn.algolia.com/api/v1/search?tags=';
fetch(`${url}${type}&query=${search_tag}`)
.then(res => res.json())
.then(data => {
this.setState({ hits: data.hits });
});
}
render() {
return (
<div>
<MenuBar />
<SearchBar onChange={this.fetchdata} />
<Articles data={this.state.hits} />
</div>
);
}
}
Have the fetchdata function in the main component and pass it to the SearchBar component as a onChange function which will be called when the search bar input will change (or a search button get pressed).
What do you think?

Could it be that inside this.props.getData() you change a state value, which is ultimately passed on as a prop? This would then cause the componentWillReceiveProps function to be re-called.
You can probably overcome this issue by checking if the search prop has changed in componentWillReceiveProps:
componentWillReceiveProps ({search}) {
if (search !== this.props.search) {
this.fetchdata(search);
}
}

accessing props inside react constructor

I am unable to get props inside constructor that I have implemented using redux concept.
Code for container component
class UpdateItem extends Component{
constructor(props) {
super(props);
console.log(this.props.item.itemTitle) // output: undefined
this.state = {
itemTitle: this.props.item.itemTitle,
errors: {}
};
this.handleChange = this.handleChange.bind(this);
}
handleChange(e) {
//If the input fields were directly within this
//this component, we could use this.refs.[FIELD].value
//Instead, we want to save the data for when the form is submitted
let state = {};
state[e.target.name] = e.target.value.trim();
this.setState(state);
}
handleSubmit(e) {
//we don't want the form to submit, so we pritem the default behavior
e.preventDefault();
let errors = {};
errors = this._validate();
if(Object.keys(errors).length != 0) {
this.setState({
errors: errors
});
return;
}
let itemData = new FormData();
itemData.append('itemTitle',this.state.itemTitle)
this.props.onSubmit(itemData);
}
componentDidMount(){
this.props.getItemByID();
}
componentWillReceiveProps(nextProps){
if (this.props.item.itemID != nextProps.item.itemID){
//Necessary to populate form when existing item is loaded directly.
this.props.getItemByID();
}
}
render(){
let {item} = this.props;
return(
<UpdateItemForm
itemTitle={this.state.itemTitle}
errors={this.state.errors}
/>
);
}
}
UpdateItem.propTypes = {
item: PropTypes.array.isRequired
};
function mapStateToProps(state, ownProps){
let item = {
itemTitle: ''
};
return {
item: state.itemReducer
};
}
function mapDispatchToProps (dispatch, ownProps) {
return {
getItemByID:()=>dispatch(loadItemByID(ownProps.params.id)),
onSubmit: (values) => dispatch(updateItem(values))
}
}
export default connect(mapStateToProps,mapDispatchToProps)(UpdateItem);
Inside render() method am able to get the props i.e. item from the redux but not inside constructor.
And code for the actions to see if the redux implementation correct or not,
export function loadItemByID(ID){
return function(dispatch){
return itemAPI.getItemByID(ID).then(item => {
dispatch(loadItemByIDSuccess(item));
}).catch(error => {
throw(error);
});
};
}
export function loadItemByIDSuccess(item){
return {type: types.LOAD_ITEM_BY_ID_SUCCESS, item}
}
Finally my reducer looks as follows,
export default function itemReducer(state = initialState.item, action) {
switch (action.type) {
case types.LOAD_ITEM_BY_ID_SUCCESS:
return Object.assign([], state = action.item, {
item: action.item
});
default:
return state;
}
}
I have googled to get answers with no luck, I don't know where i made a mistake. If some one point out for me it would be a great help. Thanks in advance.

The reason you can't access the props in the constructor is that it is only called once, before the component is first mounted.
The action to load the item is called in the componentWillMount function, which occurs after the constructor is called.
It appears like you are trying to set a default value in the mapStateToProps function but aren't using it at all
function mapStateToProps(state, ownProps){
// this is never used
let item = {
itemTitle: ''
};
return {
item: state.itemReducer
};
}
The next part I notice is that your are taking the state from redux and trying to inject it into the component's local state
this.state = {
itemTitle: this.props.item.itemTitle,
errors: {}
};
Mixing redux state and component state is very rarely a good idea and should try to be avoided. It can lead to inconsistency and and hard to find bugs.
In this case, I don't see any reason you can't replace all the uses of this.state.itemTitle with this.props.items.itemTitle and remove it completely from the component state.
Observations
There are some peculiar things about your code that make it very difficult for me to infer the intention behind the code.
Firstly the reducer
export default function itemReducer(state = initialState.item, action) {
switch (action.type) {
case types.LOAD_ITEM_BY_ID_SUCCESS:
return Object.assign([], state = action.item, {
item: action.item
});
default:
return state;
}
}
You haven't shown the initialState object, but generally it represents the whole initial state for the reducer, so using initialState.item stands out to me. You may be reusing a shared initial state object for all of the reducers so I'm not too concerned about this.
What is very confusing the Object.assign call. I'm not sure it the intention is to output an object replacing item in the state, or if it is to append action.item to an array, or to have an array with a single item as the resulting state. The state = action.item part is also particularly puzzling as to it's intention in the operation.
This is further confused by the PropTypes for UpdateItem which requires item to be an array
UpdateItem.propTypes = {
item: PropTypes.array.isRequired
};
But the usage in the component treats it like and object
this.state = {
// expected some kind of array lookup here |
// V---------------
itemTitle: this.props.item.itemTitle,
errors: {}
};
Update from comments
Here is a example of what I was talking about in the comments. It's a simplified version of your code (I don't have all your components. I've also modified a few things to match my personal style, but hopefully you can still see what's going on.