So I've rewrote my code a bit to use state instead of modifying props since it is not what I should do. The problem that occurred now is that when componentDidMount runs props are still not fetched from the backend, therefore the if statements in the function are always false.
componentDidMount() {
this.props.getTypes('sport');
this.props.getSchema();
this.props.getDomainForm();
if(Object.keys(this.props.schema).length) {
this.setState({schema: this.props.schema})
}
if(Object.keys(this.props.formData).length) {
this.setState({form: this.props.formData})
}
}
const mapStateToProps = (state) => {
return {
schema: state.admin.settings.Domains.schema.data || {},
formData: state.admin.settings.Domains.domain.data || {},
types: state.admin.settings.Domains.types.data || {},
}
};
I've stepped trough the code and it seems like componentDidMount runs only once. Since componentWillRecieveProps is deprecated I am unsure what to do to fix this, and I hope you guys can help me with this one.
PS. there is no problems with fetch actions and reducers works perfectly I haven't changed anything there and redux debugger is displaying the results correctly.
i think the problem is your fetch is async and it takes little bit time to accomplish the task, and before the fetch is been finished , your component mounts on the DOM.
as you noted you can see the data is been received via redux debugger and you have no problem with it , so i'm guessing that you passed the initial state as empty object or array to your state. so then your component receives data through props and you are not updating the state to reRender the component , what you need to do is just use componentWillReceiveProps to update the state whenever the new data is been received by just checking if current props is not equal to previous props , some code like this :
componentWillReceiveProps = (nextProps) => {
if(this.props.yourPropsFromRedux != nextProps.yourPropsFromRedux ) {
this.setState({ yourState: nextProps.yourPropsFromRedux })
}
}
As a replacement of componentWillReceiveProps there was introduced static getDerivedStateFromProps(props, state) method, it's called each time component receives new props, so it might be helpful for you. Here's the docs.
Using componentDidUpdate along with componentDidMount is more suitable for this situation. componentDidMount will set the state for initial render and componentDidUpdate will set state for future renders. Don't forget to test the prevProps parameter of the componentDidUpdate method with current props to check if the data has changed or not. Read the documentation here
Related
I'm facing an issue with Redux and React
I use a redux action to fetch data from an API. When the component mounts, this action is fired and populate the Redux state. I want a second action to be fired with parameters (article) from the redux state.
My issue is that when I fire the second action, the redux state is still empty, so article is null, which causes an error.
componentDidMount() {
const { targetArticle, userVisit, match, article } = this.props
targetArticle(match.params.slug);
userVisit(match.params.slug, article.title);
}
I've already checked other topics on the subject like this one, but none of them works for me. How can I achieve that?
Thanks
You'd probably have to use componentDidUpdate lifecycle method. So given that userVisit is dependent on the result of targetArticle and assuming you are looking to this.props. for the updated Redux state, something like this should get you there:
componentDidUpdate(prevProps) {
if(prevProps.article !== this.props.article) {
// Now you have access to targetArticle's result and updated Redux state
userVisit(match.params.slug, this.props.article.title)
}
}
More in the docs: https://reactjs.org/docs/react-component.html#componentdidupdate
I'm building a react native app and using redux to handle the state. I am running into a situation where one of my containers is not updating immediately when the redux state is changed.
Container:
...
class ContainerClass extends Component<Props, State> {
...
componentWillReceiveProps(nextProps: Object) {
console.log('WILL RECEIVE PROPS:', nextProps);
}
...
render() {
const { data } = this.props;
return <SubComponent data={data} />
}
}
const mapStateToProps = (state) => ({
data: state.data
};
export default connect(mapStateToProps)(ContainerClass);
Reducer:
...
export default function reducer(state = initalState, action) => {
switch(action.type) {
case getType(actions.actionOne):
console.log('SETTING THE STATE');
return { ...state, data: action.payload };
...
...
...
In a different random component, I am dispatching a call with the actionOne action, which I confirm prints out the relevant console.log. However, the console.log in the componentWillReceiveProps in the container is not printed.
The component that dispatches the call is a modal that has appeared over the Container, and closes automatically after the call is dispatched and the state is updated. What is weird is that although the Container isn't updated immediately, if I navigate to a different page and then back to the Container page, the state is in fact updated.
EDIT: Initial state is:
const initialState: Store = {
data: []
}
And the way I dispatch is in a different component which gets called as a new modal (using react-native-navigation) from Container:
fnc() {
...
setData(data.concat(newDatum));
...
}
Where setData and data are the redux dispatch action and the part of the store respectively that is passed in on props from the Container (which has setData and data through mapStateToProps shown above and a mapDispatchToProps which I didn't show).
I solved my problem by updating from react-native v0.56 to v0.57. Apparently there was a problem with react-redux v6 working properly in the react-native v0.56 environment.
Assuming you're using a recent version of React, componentWillReceiveProps is actually deprecated:
Using this lifecycle method often leads to bugs and inconsistencies
You can't really rely on that lifecycle hook in a number of situations. You may want to look at a slightly different approach with componentDidUpdate instead.
I think more important is to get the value after changing in state of redux rather than in which lifecycle you are getting the value . so for getting the value you can use subscribe method of redux in componentDidMount
store.subscribe( ()=> {
var updatedStoreState = store.getState();
})
I believe that getDerivedStateForProps would solve your problem.
static getDerivedStateFromProps(nextProps, prevState) {
if(nextProps.data !== prevState.data) {
//Do something
} else {
//Do something else
}
}
You would check the state from the redux against the state from your component and then act accordingly.
Also, some info from the documentation that you might consider before using this method:
1. getDerivedStateFromProps is invoked right before calling the render method, both on the initial mount and on subsequent updates.
2. This method exists for rare use cases where the state depends on changes in props over time.
3. If you need to perform a side effect (for example, data fetching or an animation) in response to a change in props, use componentDidUpdate lifecycle instead.
You can read more at: https://reactjs.org/docs/react-component.html#static-getderivedstatefromprops
I am looking at someone else code who updated the state of object in the react lifecyle:componentWillReceiveProps. I am fairly new to react and redux but thought that you do all the updating of state in the reducer useless its local state. Can someone tell me why he is doing it in componentWillReceiveProps? Thanks
componentWillReceiveProps(nextProps) {
if(this.props.isEditingbook && !nextProps.isEditingbook) {
let book = this.props.index.bookDictionary[this.props.currentbook.id]
book.name = this.state.model.name.value
}
this.setState({ ...this.state, ...nextProps})
}
Well, first of all, componentWillrecieveProps has been deprecated because it might cause some problems, take a look here . Instead, React docs point out that you should use componentDidUpdate which is a safe-to-use method.
And answering your question, if you looked a code where that person was using redux, then he used that deprecated method because when you bind a component to redux goblal state (store) through mapStateToProps, it's properties are bind to that component props. So, in other words, whenever the global state changes so does the component props, and if you want to "track" these changes in your component logic, you have to know when it's props are going to change, that's why you use componentWillRecieveProps or componentDidUpdate methods.
Here is how that example code should has been done with componentDidUpdate:
componentDidUpdate(prevProps) { //prevProps is the previous props of the component before being updated
//so, if this.props != prevProps it means that component props have been updated
if(this.props.isEditingbook && !prevProps.isEditingbook) {
let book = this.props.index.bookDictionary[this.props.currentbook.id]
book.name = this.state.model.name.value
}
this.setState({ ...this.state, ...prevProps})
}
I recently wanted to upgrade my knowledge of React, so I started from the component lifecycle methods. The first thing that got me curious, is this componentWillReceiveProps. So, the docs are saying that it's fired when component is receiving new (not necessarily updated) props. Inside that method we can compare them and save into the state if needed.
My question is: Why do we need that method, if changes in props of that component (inside parent render) will trigger the re-render of this child component?
One common use case are state (this.state) updates that may be necessary in response to the updated props.
Since you should not try to update the component's state via this.setState() in the render function, this needs to happen in componentWillReceiveProps.
Additionally, if some prop is used as a parameter to some fetch function you should watch this prop in componentWillReceiveProps to re-fetch data using the new parameter.
Usually componentDidMount is used as a place where you trigger a method to fetch some data. But if your container, for example, UserData is not unmounted and you change userId prop, the container needs to fetch data of a user for corresponding userId.
class UserData extends Component {
componentDidMount() {
this.props.getUser(this.props.userId);
}
componentWillReceiveProps(nextProps) {
if (this.props.userId !== nextProps.userid) {
this.props.getUser(nextProps.userId);
}
}
render() {
if (this.props.loading) {
return <div>Loading...</div>
}
return <div>{this.user.firstName}</div>
}
}
It is not a full working example. Let's imagine that getUser dispatch Redux action and Redux assign to the component user, loading and getUser props.
It 'serves' as an opportunity to react to the incoming props to set the state of your application before render. If your call setState after render you will re-render infinitely and that's why you're not allowed to do that, so you can use componentWillReceiveProps instead.
But... you are beyond CORRECT in your confusion, so correct in fact that they are deprecating it and other Will-lifecycle hooks Discussion Deprecation.
There are other ways to accomplish what you want to do without most of those Will-lifecycle methods, one way being don't call setState after render, just use the new incoming props directly in render (or wherever) to create the stateful value you need and then just use the new value directly, you can then later set state to keep a reference for the next iteration ex: this.state.someState = someValue, this will accomplish everything and not re-render the component in an infinite loop.
Use this as an opportunity to react to a prop transition before render() is called by updating the state using this.setState(). The old props can be accessed via this.props. Calling this.setState() within this function will not trigger an additional render.
Look at this article
the componentWillReceiveProps will always receive as param "NxtProps", componentWillReceiveProps is called after render().
some people use this method use this to compare nxtProps and this.props to check, if something should happen before the component call render, and to some validations.
check the react's documentation to know more about react lifecycle!
hope this could help you!
changes in props of that component (inside parent render) will trigger the re-render of this child component
You are absolutely right. You only need to use this method if you need to react to those changes. For instance, you might have a piece of state in a child component that is calculated using multiple props.
Small Example:
class Test extends Component {
state = {
modified: "blank"
};
componentDidMount(){
this.setState({
modified: `${this.props.myProp} isModified`
});
}
componentWillReceiveProps(nextProps) {
this.setState({
modified: `${nextProps.myProp} isModified`
});
}
render() {
return <div className="displayed">{this.state.modified}</div>
}
}
In this example, componentDidMount sets the state using this.props. When this component receives new props, without componentWillReceiveProps, this.state.modified would never be updated again.
Of course, you could just do {this.props.myProp + "IsModified"} in the render method, but componentWillReceiveProps is useful when you need to update this.state on prop changes.
I am trying to update the state of a component with new props received by the parent component.
However, the setState call doesn't seem to be working as I would expect.
I understand componentWillReceiveProps won't re-render the component, but it doesn't even seem to be allowing a setState call.
Any ideas what I might be doing wrong?
The code:
componentWillReceiveProps (nextProps) {
this.setState({name: nextProps.site.name});
console.log(nextProps.site.name); // logs the updated name
console.log(this.state.name); // logs the old name, even after presumably being set again
}
It's done asynchronously. So you may not see the update within the method. Check that in componentDidUpdate.
you can see the result in the setState callback , like this :
this.setState({name: nextProps.site.name} , ()=>{
console.log(this.state.name);
});