I would like to figure out how to subscribe on updates of a stored value it the redux store.
So far I've tried something like the following:
<ReactReduxContext.Consumer>
{({store}) => {
console.log('store:', store.getState());
const p = <p>{store.getState().value}</p>;
store.subscribe(() => {p.innerText = store.getState().value});
return p;
}}
</ReactReduxContext.Consumer>
bumping into the TypeError: can't define property "innerText": Object is not extensible error on updates.
So I wonder how to update the contents?
There are a few things about your code that are just not the way that we do things in React.
React is its own system for interacting with the DOM, so you should not attempt direct DOM manipulation through .innerText. Your code doesn't work because the variable p which you create is a React JSX Element rather than a raw HTML paragraph element, so it doesn't have properties like innerText.
Instead, you just return the correct JSX code based on props and state. The code will get updated any time that props or state change.
The ReactReduxContext is used internally by the react-redux package. Unless you have a good reason to use it in your app, I would not recommend it. There are two built-in ways that you can get a current value of state that is already subscribed to changes.
useSelector hook
(recommended)
export const MyComponent1 = () => {
const value = useSelector(state => state.value);
return <p>{value}</p>
}
connect higher-order component
(needed for class components which cannot use hooks)
class ClassComponent extends React.Component {
render() {
return <p>{this.props.value}</p>
}
}
const mapStateToProps = state => ({
value: state.value
});
const MyComponent2 = connect(mapStateToProps)(ClassComponent)
ReactReduxContext
(not recommended)
If anyone reading this has a good reason why they should need to use store.subscribe(), proper usage would look something like this:
const MyComponent3 = () => {
const { store } = useContext(ReactReduxContext);
const [state, setState] = useState(store.getState());
useEffect(() => {
let isMounted = true;
store.subscribe(() => {
if (isMounted) {
setState(store.getState());
}
});
// cleanup function to prevent calls to setState on an unmounted component
return () => {
isMounted = false;
};
}, [store]);
return <p>{state.value}</p>;
};
CodeSandbox Demo
I am using Redux with Class Components in React. Having the below two states in Redux store.
{ spinner: false, refresh: false }
In Parent Components, I have a dispatch function to change this states.
class App extends React.Component {
reloadHandler = () => {
console.log("[App] reloadComponent");
this.props.onShowSpinner();
this.props.onRefresh();
};
render() {
return <Child reloadApp={this.reloadHandler} />;
}
}
In Child Component, I am trying to reload the parent component like below.
class Child extends React.Component {
static getDerivedStateFromProps(props, state) {
if (somecondition) {
// doing some redux store update
props.reloadApp();
}
}
render() {
return <button />;
}
}
I am getting error as below.
Warning: Cannot update a component from inside the function body of a
different component.
How to remove this warning? What I am doing wrong here?
For me I was dispatching to my redux store in a React Hook. I had to dispatch in a useEffect to properly sync with the React render cycle:
export const useOrderbookSubscription = marketId => {
const { data, error, loading } = useSubscription(ORDERBOOK_SUBSCRIPTION, {
variables: {
marketId,
},
})
const formattedData = useMemo(() => {
// DISPATCHING HERE CAUSED THE WARNING
}, [data])
// DISPATCHING HERE CAUSED THE WARNING TOO
// Note: Dispatching to the store has to be done in a useEffect so that React
// can sync the update with the render cycle otherwise it causes the message:
// `Warning: Cannot update a component from inside the function body of a different component.`
useEffect(() => {
orderbookStore.dispatch(setOrderbookData(formattedData))
}, [formattedData])
return { data: formattedData, error, loading }
}
If your code calls a function in a parent component upon a condition being met like this:
const ListOfUsersComponent = ({ handleNoUsersLoaded }) => {
const { data, loading, error } = useQuery(QUERY);
if (data && data.users.length === 0) {
return handleNoUsersLoaded();
}
return (
<div>
<p>Users are loaded.</p>
</div>
);
};
Try wrapping the condition in a useEffect:
const ListOfUsersComponent = ({ handleNoUsersLoaded }) => {
const { data, loading, error } = useQuery(QUERY);
useEffect(() => {
if (data && data.users.length === 0) {
return handleNoUsersLoaded();
}
}, [data, handleNoUsersLoaded]);
return (
<div>
<p>Users are loaded.</p>
</div>
);
};
It seems that you have latest build of React#16.13.x. You can find more details about it here. It is specified that you should not setState of another component from other component.
from the docs:
It is supported to call setState during render, but only for the same component. If you call setState during a render on a different component, you will now see a warning:
Warning: Cannot update a component from inside the function body of a different component.
This warning will help you find application bugs caused by unintentional state changes. In the rare case that you intentionally want to change the state of another component as a result of rendering, you can wrap the setState call into useEffect.
Coming to the actual question.
I think there is no need of getDerivedStateFromProps in the child component body. If you want to trigger the bound event. Then you can call it via the onClick of the Child component as i can see it is a <button/>.
class Child extends React.Component {
constructor(props){
super(props);
this.updateState = this.updateState.bind(this);
}
updateState() { // call this onClick to trigger the update
if (somecondition) {
// doing some redux store update
this.props.reloadApp();
}
}
render() {
return <button onClick={this.updateState} />;
}
}
Same error but different scenario
tl;dr wrapping state update in setTimeout fixes it.
This scenarios was causing the issue which IMO is a valid use case.
const [someState, setSomeState] = useState(someValue);
const doUpdate = useRef((someNewValue) => {
setSomeState(someNewValue);
}).current;
return (
<SomeComponent onSomeUpdate={doUpdate} />
);
fix
const [someState, setSomeState] = useState(someValue);
const doUpdate = useRef((someNewValue) => {
setTimeout(() => {
setSomeState(someNewValue);
}, 0);
}).current;
return (
<SomeComponent onSomeUpdate={doUpdate} />
);
In my case I had missed the arrow function ()=>{}
Instead of onDismiss={()=>{/*do something*/}}
I had it as onDismiss={/*do something*/}
I had same issue after upgrading react and react native, i just solved that issue by putting my props.navigation.setOptions to in useEffect. If someone is facing same problen that i had i just want to suggest him put your state changing or whatever inside useEffect
Commented some lines of code, but this issue is solvable :) This warnings occur because you are synchronously calling reloadApp inside other class, defer the call to componentDidMount().
import React from "react";
export default class App extends React.Component {
reloadHandler = () => {
console.log("[App] reloadComponent");
// this.props.onShowSpinner();
// this.props.onRefresh();
};
render() {
return <Child reloadApp={this.reloadHandler} />;
}
}
class Child extends React.Component {
static getDerivedStateFromProps(props, state) {
// if (somecondition) {
// doing some redux store update
props.reloadApp();
// }
}
componentDidMount(props) {
if (props) {
props.reloadApp();
}
}
render() {
return <h1>This is a child.</h1>;
}
}
I got this error using redux to hold swiperIndex with react-native-swiper
Fixed it by putting changeSwiperIndex into a timeout
I got the following for a react native project while calling navigation between screens.
Warning: Cannot update a component from inside the function body of a different component.
I thought it was because I was using TouchableOpacity. This is not an issue of using Pressable, Button, or TouchableOpacity. When I got the error message my code for calling the ChatRoom screen from the home screen was the following:
const HomeScreen = ({navigation}) => {
return (<View> <Button title = {'Chats'} onPress = { navigation.navigate('ChatRoom')} <View>) }
The resulting behavior was that the code gave out that warning and I couldn't go back to the previous HomeScreen and reuse the button to navigate to the ChatRoom. The solution to that was doing the onPress in an inline anonymous function.
onPress{ () => navigation.navigate('ChatRoom')}
instead of the previous
onPress{ navigation.navigate('ChatRoom')}
so now as expected behavior, I can go from Home to ChatRoom and back again with a reusable button.
PS: 1st answer ever in StackOverflow. Still learning community etiquette. Let me know what I can improve in answering better. Thanx
If you want to invoke some function passed as props automatically from child component then best place is componentDidMount lifecycle methods in case of class components or useEffect hooks in case of functional components as at this point component is fully created and also mounted.
I was running into this problem writing a filter component with a few text boxes that allows the user to limit the items in a list within another component. I was tracking my filtered items in Redux state. This solution is essentially that of #Rajnikant; with some sample code.
I received the warning because of following. Note the props.setFilteredItems in the render function.
import {setFilteredItems} from './myActions';
const myFilters = props => {
const [nameFilter, setNameFilter] = useState('');
const [cityFilter, setCityFilter] = useState('');
const filterName = record => record.name.startsWith(nameFilter);
const filterCity = record => record.city.startsWith(cityFilter);
const selectedRecords = props.records.filter(rec => filterName(rec) && filterCity(rec));
props.setFilteredItems(selectedRecords); // <-- Danger! Updates Redux during a render!
return <div>
<input type="text" value={nameFilter} onChange={e => setNameFilter(e.target.value)} />
<input type="text" value={cityFilter} onChange={e => setCityFilter(e.target.value)} />
</div>
};
const mapStateToProps = state => ({
records: state.stuff.items,
filteredItems: state.stuff.filteredItems
});
const mapDispatchToProps = { setFilteredItems };
export default connect(mapStateToProps, mapDispatchToProps)(myFilters);
When I ran this code with React 16.12.0, I received the warning listed in the topic of this thread in my browser console. Based on the stack trace, the offending line was my props.setFilteredItems invocation within the render function. So I simply enclosed the filter invocations and state change in a useEffect as below.
import {setFilteredItems} from './myActions';
const myFilters = props => {
const [nameFilter, setNameFilter] = useState('');
const [cityFilter, setCityFilter] = useState('');
useEffect(() => {
const filterName = record => record.name.startsWith(nameFilter);
const filterCity = record => record.city.startsWith(cityFilter);
const selectedRecords = props.records.filter(rec => filterName(rec) && filterCity(rec));
props.setFilteredItems(selectedRecords); // <-- OK now; effect runs outside of render.
}, [nameFilter, cityFilter]);
return <div>
<input type="text" value={nameFilter} onChange={e => setNameFilter(e.target.value)} />
<input type="text" value={cityFilter} onChange={e => setCityFilter(e.target.value)} />
</div>
};
const mapStateToProps = state => ({
records: state.stuff.items,
filteredItems: state.stuff.filteredItems
});
const mapDispatchToProps = { setFilteredItems };
export default connect(mapStateToProps, mapDispatchToProps)(myFilters);
When I first added the useEffect I blew the top off the stack since every invocation of useEffect caused state change. I had to add an array of skipping effects so that the effect only ran when the filter fields themselves changed.
I suggest looking at video below. As the warning in the OP's question suggests, there's a change detection issue with the parent (Parent) attempting to update one child's (Child 2) attribute prematurely as the result of another sibling child's (Child 1) callback to the parent. For me, Child 2 was prematurely/incorrectly calling the passed in Parent callback thus throwing the warning.
Note, this commuincation workflow is only an option. I personally prefer exchange and update of data between components via a shared Redux store. However, sometimes it's overkill. The video suggests a clean alternative where the children are 'dumb' and only converse via props mand callbacks.
Also note, If the callback is invoked on an Child 1 'event' like a button click it'll work since, by then, the children have been updated. No need for timeouts, useEffects, etc. UseState will suffice for this narrow scenario.
Here's the link (thanks Masoud):
https://www.youtube.com/watch?v=Qf68sssXPtM
In react native, if you change the state yourself in the code using a hot-reload I found out I get this error, but using a button to change the state made the error go away.
However wrapping my useEffect content in a :
setTimeout(() => {
//....
}, 0);
Worked even for hot-reloading but I don't want a stupid setTimeout for no reason so I removed it and found out changing it via code works just fine!
I was updating state in multiple child components simultaneously which was causing unexpected behavior. replacing useState with useRef hook worked for me.
Try to use setTimeout,when I call props.showNotification without setTimeout, this error appear, maybe everything run inTime in life circle, UI cannot update.
const showNotifyTimeout = setTimeout(() => {
this.props.showNotification();
clearTimeout(showNotifyTimeout);
}, 100);
Prefacing this with a thought; I think I might require a recursive component but that's beyond my current ability with native js and React so I feel like I have Swiss cheese understanding of React at this point.
The problem:
I have an array of metafields containing metafield objects with the following structure:
{
metafields: [
{ 0:
{ namespace: "namespaceVal",
key: "keyVal",
val: [
0: "val1",
1: "val2",
2: "val3"
]
}
},
...
]
}
My code maps metafields into Cards and within each card lives a component <MetafieldInput metafields={metafields['value']} /> and within that component the value array gets mapped to input fields. Overall it looks like:
// App
render() {
const metafields = this.state.metafields;
return (
{metafields.map(metafield) => (
<MetafieldInputs metafields={metafield['value']} />
)}
)
}
//MetafieldInputs
this.state = { metafields: this.props.metafields}
render() {
const metafields = this.state;
return (
{metafields.map((meta, i) => (
<TextField
value={meta}
changeKey={meta}
onChange={(val) => {
this.setState(prevState => {
return { metafields: prevState.metafields.map((field, j) => {
if(j === i) { field = val; }
return field;
})};
});
}}
/>
))}
)
}
Up to this point everything displays correctly and I can change the inputs! However the change happens one at a time, as in I hit a key then I have to click back into the input to add another character. It seems like everything gets re-rendered which is why I have to click back into the input to make another change.
Am I able to use components in this way? It feels like I'm working my way into nesting components but everything I've read says not to nest components. Am I overcomplicating this issue? The only solution I have is to rip out the React portion and take it to pure javascript.
guidance would be much appreciated!
My suggestion is that to out source the onChange handler, and the code can be understood a little bit more easier.
Mainly React does not update state right after setState() is called, it does a batch job. Therefore it can happen that several setState calls are accessing one reference point. If you directly mutate the state, it can cause chaos as other state can use the updated state while doing the batch job.
Also, if you out source onChange handler in the App level, you can change MetafieldInputs into a functional component rather than a class-bases component. Functional based component costs less than class based component and can boost the performance.
Below are updated code, tested. I assume you use Material UI's TextField, but onChangeHandler should also work in your own component.
// Full App.js
import React, { Component } from 'react';
import MetafieldInputs from './MetafieldInputs';
class App extends Component {
state = {
metafields: [
{
metafield:
{
namespace: "namespaceVal",
key: "keyVal",
val: [
{ '0': "val1" },
{ '1': "val2" },
{ '2': "val3" }
]
}
},
]
}
// will never be triggered as from React point of view, the state never changes
componentDidUpdate() {
console.log('componentDidUpdate')
}
render() {
const metafields = this.state.metafields;
const metafieldsKeys = Object.keys(metafields);
const renderInputs = metafieldsKeys.map(key => {
const metafield = metafields[key];
return <MetafieldInputs metafields={metafield.metafield.val} key={metafield.metafield.key} />;
})
return (
<div>
{renderInputs}
</div>
)
}
}
export default App;
// full MetafieldInputs
import React, { Component } from 'react'
import TextField from '#material-ui/core/TextField';
class MetafieldInputs extends Component {
state = {
metafields: this.props.metafields
}
onChangeHandler = (e, index) => {
const value = e.target.value;
this.setState(prevState => {
const updateMetafields = [...prevState.metafields];
const updatedFields = { ...updateMetafields[index] }
updatedFields[index] = value
updateMetafields[index] = updatedFields;
return { metafields: updateMetafields }
})
}
render() {
const { metafields } = this.state;
// will always remain the same
console.log('this.props', this.props)
return (
<div>
{metafields.map((meta, i) => {
return (
<TextField
value={meta[i]}
changekey={meta}
onChange={(e) => this.onChangeHandler(e, i)}
// generally it is not a good idea to use index as a key.
key={i}
/>
)
}
)}
</div>
)
}
}
export default MetafieldInputs
Again, IF you out source the onChangeHandler to App class, MetafieldInputs can be a pure functional component, and all the state management can be done in the App class.
On the other hand, if you want to keep a pure and clean App class, you can also store metafields into MetafieldInputs class in case you might need some other logic in your application.
For instance, your application renders more components than the example does, and MetafieldInputs should not be rendered until something happened. If you fetch data from server end, it is better to fetch the data when it is needed rather than fetching all the data in the App component.
You need to do the onChange at the app level. You should just pass the onChange function into MetaFieldsInput and always use this.props.metafields when rendering
I have some components in my app which are expected to handle some user inputs from the keyboard. For that I created the following function:
export default function withKeydownEventHandler (handler) {
id = id + 1
return lifecycle({
componentWillMount () {
$(window).on(`keydown.${id}`, evt => handler(evt))
},
componentWillUnmount () {
$(window).off(`keydown.${id}`)
}
})
}
This works fine, but the handlers are being fired off for different components at the same time. So if my handler does different things in each component, whenever I click a button it will be fired off from both components at the same time. Also, once one component is unmounted, the HoC will no longer work.
For example, say I have the following two containers:
export default compose(
withKeydownEventHandler((evt, props) => {
console.warn('hi from Component 1')
}),
withProps(() => {
// stuff
})
)(Component1)
export default compose(
withKeydownEventHandler((evt, props) => {
console.warn('hi from Component 2')
}),
withProps(() => {
// stuff
})
)(Component2)
If I click any button throughout the app, I will get the following output:
hi from Component 1
hi from Component 2
On the flip side, once one of the components becomes unmounted, I no longer get any events.
What am I doing wrong? How can I get a keydown event handler through an HoC that can be re-used throughout my app?
Firstly, may I bring to your attention that your id is set as a global variable. Are you sure you want to have such a variable name as a global?
Secondly, you are binding the keydown event to the windows with $(window).on('keydown.${id}', evt => handler(evt)) which explains your unwanted behaviour. You need to bind it once with the specific component you want the handler to act to.
Finally, why dont you create a HOC class and add the event listeners conditionally? like the following:
// src/Hoc.jsx
export default function(WrapperComponent) {
return class extends Component {
componentWillMount () {
const { onKeyDownHandler } = this.props;
if (isKeyDownEventNeeded) {
this.comp.addEventListener("keydown", onKeyDownHandler);
}
}
componentWillUnmount () {
const { onKeyDownHandler } = this.props;
if (isKeyDownEventNeeded) {
this.comp.removeEventListener("keydown", onKeyDownHandler);
}
}
render() {
const { onKeyDownHandler } = this.props;
if (onKeyDownHandler) {
// a "ref" callback which assigns the mounted
// Element to a prop "comp" whicu can be used later to add the DOM listener to.
return <WrapperComponent ref={elem => this.comp = elem} {...this.props} />
}
return <WrapperComponent {...this.props} />
}
}
export default HighOrderComponent;
Then
// somewhere-else.js
import highOrderComponent from 'src/Hoc'
highOrderComponent(<Component1 onKeyDownHandler={() => console.log('hey, Component 1'} />
highOrderComponent(<Component2 onKeyDownHandler={() => console.log('hey, Component 2'} />
For more info on how check out this answer
I have a lot of components, that require some ajax function being sent, in the componentDidMount method. I would like to create a HOC, whose sole purpose is to "apply" some animation to the component, and stop this animation once a certain promise is resolved.
Of course, i could just copy paste this code for each component, but i would like to create some abstraction that deals with it.
The problem is, that i don't know how to pass the function properly, from the child to the parent. For instance, let's assume the intended child component, has this componentDidMount:
componentDidMount() {
ajax('/costumers')
.then(({ data }) => {
this.setState(() => ({ costumers: data.content }))
})
}
Technically, i need to either pass this function as an argument to the HOC, or perhaps somehow "hijack" the child's componentDidMount(if something like that is possible...). The HOC would then apply an animation once it's loaded, then send the ajax, and only when it's solved, the animation is eliminated, and the child component gets rendered.
How can this be achieved?
Any idea will be appreciated
Here is how you can write a HOC for such a case, refer to React docs for more info on the subject.
const withLoader = (loader, Component) =>
class WithLoader extends React.Component {
state = { ready: false, data: null };
async componentDidMount() {
const data = await loader();
this.setState({ ready: true, data });
}
render() {
if (!this.state.ready) return <div>LOADING</div>; // or <ComponentWithAnimation />
return <Component data={this.state.data} />;
}
};
const Test = props => <div>DATA: {props.data}</div>;
const fakeLoader = () =>
new Promise(res => setTimeout(() => res("My data"), 1000));
const TestWithLoader = withLoader(fakeLoader, Test);