I am working on an application and when i had the ...this.state in my componentWillRecieveProps my code was not working correctly.
I am not 100% sure why this was affecting my state. Is it because i am always appending the current state when theres no need to do that.
componentWillReceiveProps(nextProps) {
// this.setState({ ...this.state, ...nextProps })
this.setState({...nextProps})
}
The componentWillReceiveProps lifecycle function is deprecated. Please use the getDerivedStateFromProps static method instead. In your case it will look like this:
class Example extends React.Component {
state = {
...
}
static getDerivedStateFromProps(nextProps) {
return {...nextProps}
}
render() {
...
}
}
However in real life it is aimless to convert every props to state without using any logic. In this case it is better to reach the props directly via this.props.
Related
I m building an appointment application with react native,its my first try in RC,Using react-redux to manage the state.I need some clarification about lifecycle methods.
Details.js
class Details extends Component {
constructor(props) {
super(props);
}
componentDidMount(){
this.props.bookingAndSuggestions(Data)
}
componentWillReceiveProps(nextProps){
if( Object.keys(nextProps.bookingSuggestionStatus).length >0) {
if(nextProps.bookingSuggestionStatus.res.data.status=='available') {
this.setState({isAvailable:false})
} else {
this.setState({isAvailable:true})
}} }
onBookNow=()=>{
this.props.shops(Data);
}
Here is the deal,Initially i call react-redux action prop this.props.bookingAndSuggestions(Data) and i capture the response inside componentWillReceiveProps,and On booking this.props.shops(Data); will trigger and it also updates the componentWillrecieveprops,the logic inside the componentwillrecieveprops updates each time when props changes.What is the proper approach to deal with such situation?
componentWillReceiveProps is called not only when the props change but also when the parent re-renders and hence whenever it is being called the state is being evaulated and set again.
You have two options
If you aren't modifying the isAvailable state internally, you could simply use it from props directly.
Eg:
const isAvailable = this.props.bookingSuggestionStatus && this.props.bookingSuggestionStatus.res.data.status=='available'
If you are modifying it, then you need to check if the props have changed which you can do in componentWillReceiveProps(use getDerivedStateFromProps from v16.3.0 onwards)
Eg:
componentWillReceiveProps(nextProps){
if(!_.isEqual(nextProps.bookingSuggestionStatus, this.props.bookingSuggestionStatus) && Object.keys(nextProps.bookingSuggestionStatus).length >0) {
if(nextProps.bookingSuggestionStatus.res.data.status=='available') {
this.setState({isAvailable:false})
} else {
this.setState({isAvailable:true})
}
}
}
Before upgrading react to version 16.3, I'd call a method based on changes in props like this :
componentWillReceiveProps(nextProps){
if(this.props.country.length !== nextProps.country){
doSomething(); //example calling redux action
}
}
componentWillReceiveProps is unsafe on Version 16.3 and we must use getDerivedStateFromProps. However, this method returns an object and I don't know how I can call a method from inside it the same way I do with componentWillReceiveProps
Yes, you need to return an object, which is the new state that that is derived from nextProp. According to docs:
getDerivedStateFromProps should return an object to update state, or null to indicate that the new props do not require any state updates.
But since you are not updating your state in any way inside your componentWillReceiveProps, you should use componentDidUpdate instead of getDerivedStateFromProps:
componentDidUpdate(prevProps){
if ( prevProps.country !== this.props.country.length ) {
doSomething(); //example calling redux action
}
}
For this situation, it was good for the OP to use componentDidUpdate but I found myself needing getDerivedStateFromProps so I had to make my custom function static as well and call it using the class' name inside getDerivedStateFromProps. Something like this:
componentDidMount() {
const something = ClassComponentName.runThisFunction();
this.setState({ updatedSomething: something });
}
static getDerivedStateFromProps(nextProps, prevState) {
if (nextProps.key !== prevState.key) {
return {
updatedSomething: ClassComponentName.runThisFunction()
};
}
return null;
}
static runThisFunction() {
//do stuff and return value
}
To clarify, this is updating the component's state on load as well as when new props arrive. This definitely took me back to my typed-language days. Hope it helps!
if you need to call a function in "getDerivedStateFromProps", you can put this function in state in constructor , then get this function in "getDerivedStateFromProps" from state.
put function in state in constructor:
constructor(props){
super(props);
this.state = {
func1:this.func1.bind(this)
}
}
get function from state in getDerivedStateFromProps:
getDerivedStateFromProps(props,state){
return {
model:state.func1(props.model)
}
}
I'm attempting to make a nice ApiWrapper component to populate data in various child components. From everything I've read, this should work: https://jsfiddle.net/vinniejames/m1mesp6z/1/
class ApiWrapper extends React.Component {
constructor(props) {
super(props);
this.state = {
response: {
"title": 'nothing fetched yet'
}
};
}
componentDidMount() {
this._makeApiCall(this.props.endpoint);
}
_makeApiCall(endpoint) {
fetch(endpoint).then(function(response) {
this.setState({
response: response
});
}.bind(this))
}
render() {
return <Child data = {
this.state.response
}
/>;
}
}
class Child extends React.Component {
constructor(props) {
super(props);
this.state = {
data: props.data
};
}
render() {
console.log(this.state.data, 'new data');
return ( < span > {
this.state.data.title
} < /span>);
};
}
var element = < ApiWrapper endpoint = "https://jsonplaceholder.typicode.com/posts/1" / > ;
ReactDOM.render(
element,
document.getElementById('container')
);
But for some reason, it seems the child component is not updating when the parent state changes.
Am I missing something here?
There are two issues with your code.
Your child component's initial state is set from props.
this.state = {
data: props.data
};
Quoting from this SO Answer:
Passing the intial state to a component as a prop is an anti-pattern
because the getInitialState (in our case the constuctor) method is only called the first time the
component renders. Never more. Meaning that, if you re-render that
component passing a different value as a prop, the component
will not react accordingly, because the component will keep the state
from the first time it was rendered. It's very error prone.
So if you can't avoid such a situation the ideal solution is to use the method componentWillReceiveProps to listen for new props.
Adding the below code to your child component will solve your problem with Child component re-rendering.
componentWillReceiveProps(nextProps) {
this.setState({ data: nextProps.data });
}
The second issue is with the fetch.
_makeApiCall(endpoint) {
fetch(endpoint)
.then((response) => response.json()) // ----> you missed this part
.then((response) => this.setState({ response }));
}
And here is a working fiddle: https://jsfiddle.net/o8b04mLy/
If the above solution has still not solved your problem I'll suggest you see once how you're changing the state, if you're not returning a new object then sometimes react sees no difference in the new previous and the changed state, it's a good practice to always pass a new object when changing the state, seeing the new object react will definitely re-render all the components needing that have access to that changed state.
For example: -
Here I'll change one property of an array of objects in my state, look at how I spread all the data in a new object. Also, the code below might look a bit alien to you, it's a redux reducer function BUT don't worry it's just a method to change the state.
export const addItemToCart = (cartItems,cartItemToBeAdded) => {
return cartItems.map(item => {
if(item.id===existingItem.id){
++item.quantity;
}
// I can simply return item but instead I spread the item and return a new object
return {...item}
})
}
Just make sure you're changing the state with a new object, even if you make a minor change in the state just spread it in a new object and then return, this will trigger rendering in all the appropriate places.
Hope this helped. Let me know if I'm wrong somewhere :)
There are some things you need to change.
When fetch get the response, it is not a json.
I was looking for how can I get this json and I discovered this link.
By the other side, you need to think that constructor function is called only once.
So, you need to change the way that you retrieve the data in <Child> component.
Here, I left an example code: https://jsfiddle.net/emq1ztqj/
I hope that helps.
Accepted answer and componentWillReceiveProps
The componentWillReceiveProps call in accepted answer is deprecated and will be removed from React with version 17 React Docs: UNSAFE_componentWillReceiveProps()
Using derived state logic in React
As the React docs is pointing, using derived state (meaning: a component reflecting a change that is happened in its props) can make your components harder to think, and could be an anti-pattern. React Docs: You Probably Don't Need Derived State
Current solution: getDerivedStateFromProps
If you choose to use derived state, current solution is using getDerivedStateFromProps call as #DiogoSanto said.
getDerivedStateFromProps is invoked right before calling the render method, both on the initial mount and on subsequent updates. It should return an object to update the state, or null to update nothing. React Docs: static getDerivedStateFromProps()
How to use componentWillReceiveProps
This method can not access instance properties. All it does describing React how to compute new state from a given props. Whenever props are changed, React will call this method and will use the object returned by this method as the new state.
class Child extends React.Component {
constructor() {
super(props);
// nothing changed, assign the state for the
// first time to teach its initial shape.
// (it will work without this, but will throw
// a warning)
this.state = {
data: props.data
};
}
componentWillReceiveProps(props) {
// return the new state as object, do not call .setState()
return {
data: props.data
};
}
render() {
// nothing changed, will be called after
// componentWillReceiveProps returned the new state,
// each time props are updated.
return (
<span>{this.state.data.title}</span>
);
}
}
Caution
Re-rendering a component according to a change happened in parent component can be annoying for user because of losing the user input on that component.
Derived state logic can make components harder to understand, think on. Use wisely.
in my react component, I have two attributes in the state, one in local react state and the other in Redux store.
componentWillMount() {
this.props.fetchExercise(this.props.params.id);
}
constructor(props) {
super(props);
this.state = {editeMode: false}
}
function mapStateToProps(state) {
return {currentExercise: state.currentExercise}
}
export default connect(mapStateToProps, {fetchExercise})(createNewExercisePage);
so according to the path; /new-exe/:id currentExercise in Redux is either empty or something is fetched. editeMode is in React. now I want to check if I have something in currentExercise editemode:true else it should be false (according to false and true I am showing different buttons).
I tried it (with lodash) in componentWillMount(){... this.setState({editeMode:_.isNull(this.props.currentExercise)})}
but it does not work, it reamins false.
generaly in these cases that first should fetch something then check it, what should be the approach.
You should avoid introducing any side-effects or subscriptions in componentWillMount (docs). The documentation also says that "setting state in this method will not trigger a re-rendering", so I guess that means that the setted value will be ignored.
You are not going to change the value of the editeMode entry in the store unless the value of this.props.currentExercise changes, and so it does not serve much purpose to keep track of the changes in order to update the store. Just use the value directly. In your particular case, I would do the following:
componentWillMount() {
this.props.fetchExercise(this.props.params.id);
}
constructor(props) {
super(props);
this.state = {}
}
render(){
const editeMode = _.isNull(this.props.currentExercise);
// The rest of your render logic, using editeMode instead of this.state.editeMode
}
function mapStateToProps(state) {
return {currentExercise: state.currentExercise}
}
export default connect(mapStateToProps, {fetchExercise})(createNewExercisePage);
Put the code in
componentWillReceiveProps.
componentWillReceiveProps(nextProps) {
this.setState({ editeMode: !nextProps.currentExercise) });
}
Redux will make sure the props get updated.
You should also consider putting the editMode state in Redux instead.
I'm trying to separate a presentational component from a container component. I have a SitesTable and a SitesTableContainer. The container is responsible for triggering redux actions to fetch the appropriate sites based on the current user.
The problem is the current user is fetched asynchronously, after the container component gets rendered initially. This means that the container component doesn't know that it needs to re-execute the code in its componentDidMount function which would update the data to send to the SitesTable. I think I need to re-render the container component when one of its props(user) changes. How do I do this correctly?
class SitesTableContainer extends React.Component {
static get propTypes() {
return {
sites: React.PropTypes.object,
user: React.PropTypes.object,
isManager: React.PropTypes.boolean
}
}
componentDidMount() {
if (this.props.isManager) {
this.props.dispatch(actions.fetchAllSites())
} else {
const currentUserId = this.props.user.get('id')
this.props.dispatch(actions.fetchUsersSites(currentUserId))
}
}
render() {
return <SitesTable sites={this.props.sites}/>
}
}
function mapStateToProps(state) {
const user = userUtils.getCurrentUser(state)
return {
sites: state.get('sites'),
user,
isManager: userUtils.isManager(user)
}
}
export default connect(mapStateToProps)(SitesTableContainer);
You have to add a condition in your componentDidUpdate method.
The example is using fast-deep-equal to compare the objects.
import equal from 'fast-deep-equal'
...
constructor(){
this.updateUser = this.updateUser.bind(this);
}
componentDidMount() {
this.updateUser();
}
componentDidUpdate(prevProps) {
if(!equal(this.props.user, prevProps.user)) // Check if it's a new user, you can also use some unique property, like the ID (this.props.user.id !== prevProps.user.id)
{
this.updateUser();
}
}
updateUser() {
if (this.props.isManager) {
this.props.dispatch(actions.fetchAllSites())
} else {
const currentUserId = this.props.user.get('id')
this.props.dispatch(actions.fetchUsersSites(currentUserId))
}
}
Using Hooks (React 16.8.0+)
import React, { useEffect } from 'react';
const SitesTableContainer = ({
user,
isManager,
dispatch,
sites,
}) => {
useEffect(() => {
if(isManager) {
dispatch(actions.fetchAllSites())
} else {
const currentUserId = user.get('id')
dispatch(actions.fetchUsersSites(currentUserId))
}
}, [user]);
return (
return <SitesTable sites={sites}/>
)
}
If the prop you are comparing is an object or an array, you should use useDeepCompareEffect instead of useEffect.
componentWillReceiveProps() is going to be deprecated in the future due to bugs and inconsistencies. An alternative solution for re-rendering a component on props change is to use componentDidUpdate() and shouldComponentUpdate().
componentDidUpdate() is called whenever the component updates AND if shouldComponentUpdate() returns true (If shouldComponentUpdate() is not defined it returns true by default).
shouldComponentUpdate(nextProps){
return nextProps.changedProp !== this.state.changedProp;
}
componentDidUpdate(props){
// Desired operations: ex setting state
}
This same behavior can be accomplished using only the componentDidUpdate() method by including the conditional statement inside of it.
componentDidUpdate(prevProps){
if(prevProps.changedProp !== this.props.changedProp){
this.setState({
changedProp: this.props.changedProp
});
}
}
If one attempts to set the state without a conditional or without defining shouldComponentUpdate() the component will infinitely re-render
You could use KEY unique key (combination of the data) that changes with props, and that component will be rerendered with updated props.
componentWillReceiveProps(nextProps) { // your code here}
I think that is the event you need. componentWillReceiveProps triggers whenever your component receive something through props. From there you can have your checking then do whatever you want to do.
I would recommend having a look at this answer of mine, and see if it is relevant to what you are doing. If I understand your real problem, it's that your just not using your async action correctly and updating the redux "store", which will automatically update your component with it's new props.
This section of your code:
componentDidMount() {
if (this.props.isManager) {
this.props.dispatch(actions.fetchAllSites())
} else {
const currentUserId = this.props.user.get('id')
this.props.dispatch(actions.fetchUsersSites(currentUserId))
}
}
Should not be triggering in a component, it should be handled after executing your first request.
Have a look at this example from redux-thunk:
function makeASandwichWithSecretSauce(forPerson) {
// Invert control!
// Return a function that accepts `dispatch` so we can dispatch later.
// Thunk middleware knows how to turn thunk async actions into actions.
return function (dispatch) {
return fetchSecretSauce().then(
sauce => dispatch(makeASandwich(forPerson, sauce)),
error => dispatch(apologize('The Sandwich Shop', forPerson, error))
);
};
}
You don't necessarily have to use redux-thunk, but it will help you reason about scenarios like this and write code to match.
A friendly method to use is the following, once prop updates it will automatically rerender component:
render {
let textWhenComponentUpdate = this.props.text
return (
<View>
<Text>{textWhenComponentUpdate}</Text>
</View>
)
}
You could use the getDerivedStateFromProps() lifecyle method in the component that you want to be re-rendered, to set it's state based on an incoming change to the props passed to the component. Updating the state will cause a re-render. It works like this:
static getDerivedStateFromProps(nextProps, prevState) {
return { myStateProperty: nextProps.myProp};
}
This will set the value for myStateProperty in the component state to the value of myProp, and the component will re-render.
Make sure you understand potential implications of using this approach. In particular, you need to avoid overwriting the state of your component unintentionally because the props were updated in the parent component unexpectedly. You can perform checking logic if required by comparing the existing state (represented by prevState), to any incoming props value(s).
Only use an updated prop to update the state in cases where the value from props is the source of truth for the state value. If that's the case, there may also be a simpler way to achieve what you need. See - You Probably Don't Need Derived State – React Blog.