I'm unable to get the props values from Redux, I checked in reducers, store, action JS files everything working fine. Even I can see the state printed correctly in console.log("MAPSTOSTATEPROPS", state) inside mapsStateToProps function below.
But when I give this.props.posts to access the values I'm not getting them. Not sure, where I'm doing wrong here. Can someone help me?
posts.js:
class Posts extends Component {
componentWillMount() {
this.props.fetchPosts();
**console.log(this.props.posts); // gives empty array result**
}
render() {
return (
<div>
<h2>Posts</h2>
</div>
)
}
componentDidMount() {
console.log("DID mount", this.props);
}
}
Posts.propTypes = {
fetchPosts: PropTypes.func.isRequired,
posts: PropTypes.array
}
const mapsStateToprops = (state) => {
**console.log("MAPSTOSTATEPROPS", state)** // gives correct result from current state
return {
posts: state.items
}
};
export default connect(mapsStateToprops, {fetchPosts}) (Posts);
class Posts extends Component {
/* use did mount method because all will-methods
are will be deprecated in nearest future */
componentDidMount() {
/* on component mount you initiate async loading data to redux store */
this.props.fetchPosts();
/* right after async method you cannot expect to retrieve your data immediately so this.props.posts will return [] */
console.log(this.props.posts);
}
render() {
/* here you getting posts from props*/
const { posts } = this.props;
return (
<div>
<h2>Posts</h2>
/* here you render posts. After async method will be completed
and dispatch action with retrieved data that will cause rerender
of component with new props */
{posts.map(post => (<div>post.name</div>))}
</div>
)
}
}
Posts.propTypes = {
fetchPosts : PropTypes.func.isRequired,
posts : PropTypes.array
}
const mapsStateToprops = (state) => {
/* first call will log an empty array of items,
but on second render after loading items to store they will
appear in component props */
console.log("MAPSTOSTATEPROPS", state)
return {
posts : state.items || [];
}
This may be because of async nature of fetchPost() method.Try to log it inside render() and handle the async nature using promises.
Related
Parent component does rerender upon receiving new props but its child component doesn't rerender. Child components only render for the first time and never rerender nor receive props from the redux store
I'm getting updated data from redux store in Parent component but not in the child components. Child components only receive data from redux store when they render for the first time
My Parent Component Home.js
Object seaFCLJSON look like this
const seaFCLJSON ={"rates": {"sort":"faster", "someOther": "someOtherValues"}};
when the redux store gets updated, seaFCLJSON looks like this
const seaFCLJSON ={"rates": {"sort":"cheaper","someOther": "someOtherValues"}};
class Home extends Component {
state = {
seaFCLJSON: {}
};
componentDidMount = () => {
this.setState({ seaFCLJSON: this.props.seaFCLJSON });
};
componentWillReceiveProps = nextProps => {
if (this.state.seaFCLJSON !== nextProps.seaFCLJSON) {
this.setState({ seaFCLJSON: nextProps.seaFCLJSON });
}
};
render() {
const { seaFCLJSON } = this.props;
return (
<>
{!isEmpty(seaFCLJSON) && seaFCLJSON.rates && seaFCLJSON.rates.fcl ? (
<FCLContainer fclJSON={seaFCLJSON} />
) : null} //it never rerenders upon getting updated data from redux store
<h5>{JSON.stringify(seaFCLJSON.rates && seaFCLJSON.rates.sort)}</h5> //it rerenders everytime upon getting updated data from redux store
</>
);
}
}
const mapStateToProps = state => {
return {
seaFCLJSON: state.route.seaFCLJSON
};
};
export default connect(
mapStateToProps,
actions
)(Home);
isEmpty.js
export const isEmpty = obj => {
return Object.entries(obj).length === 0 && obj.constructor === Object;
};
My Child Component FCLContainer.js
class FCLContainer extends Component {
state = {
seaFCLJSON: {}
};
componentDidMount = () => {
this.setState({ seaFCLJSON: this.props.seaFCLJSON });
};
componentWillReceiveProps = nextProps => {
console.log("outside state value: ", this.state.seaFCLJSON);
if (this.state.seaFCLJSON !== nextProps.seaFCLJSON) {
this.setState({ seaFCLJSON: nextProps.seaFCLJSON });
console.log("inside state value: ", this.state.seaFCLJSON);
}
};
render() {
const { seaFCLJSON } = this.state;
console.log("rendering .. parent props: ", this.props.fclJSON);
console.log("rendering .. redux store props: ", this.props.seaFCLJSON);
return (
<>
<div className="home-result-container">
<div>
<h5>This child component never rerenders :(</h5>
</div>
</div>
</>
);
}
}
const mapStateToProps = state => {
return {
seaFCLJSON: state.route.seaFCLJSON
};
};
export default connect(
mapStateToProps,
actions
)(FCLContainer);
I don't know whether there are problems in Parent component or problems in the child component. componentWillReceiveProps gets invoked in the parent component but not in the child component. Please ignore any missing semi-colon or braces because I have omitted some unnecessary codes.
Edit 1: I just duplicated value from props to state just for debugging purposes.
I will appreciate your help. Thank you.
Edit 2: I was directly changing an object in redux actions. That's the reason CWRP was not getting fired. It was the problem. For more check out my answer below.
componentWillReceiveProps will be deprecated in react 17, use componentDidUpdate instead, which is invoked immediately after updating occurs
Try something like this:
componentDidUpdate(prevProps, prevState) {
if (this.prevProps.seaFCLJSON !== this.props.seaFCLJSON) {
this.setState({ seaFCLJSON: this.props.seaFCLJSON });
}
};
At the first place it is absolutely meaningless to duplicate value from props to state, what is the meaning of it? Totally pointless, just keep it in props
About your issue - most probably this condition doesnt match, thats why child component doesnt trigger
!isEmpty(seaFCLJSON) && seaFCLJSON.rates && seaFCLJSON.rates.fcl
check it in debugger
As far as I can see, your problem is that you pass the following to your child component:
<FCLContainer fclJSON={seaFCLJSON} />
But you assume that you receive a prop called 'seaFCLJSON':
componentDidMount = () => {
this.setState({ seaFCLJSON: this.props.seaFCLJSON });
};
You should change your code to:
<FCLContainer seaFCLJSON={seaFCLJSON} />
Apart from that, as #Paul McLoughlin already mentioned, you should use the prop directly instead of adding it to your state.
I found the issue I was directly mutating the object in actions. I only knew state should not be directly mutated in class or inside reducer. I changed the actions where I was directly changing an object and then saving it in redux store via dispatch and, then I received the updated props in CWRP. This really took me a lot of times to figure out. This kind of issue is hard to find out at least for me. I guess I get this from https://github.com/uberVU/react-guide/issues/17
A lesson I learned: Never directly mutate an Object
I changed this
//FCL sort by faster
export const sortByFasterFCLJSON = () => async (dispatch, getState) => {
let seaFCLJSON = getState().route.seaFCLJSON;
if (!seaFCLJSON.rates) return;
seaFCLJSON.rates.fcl = _.orderBy(
seaFCLJSON.rates.fcl,
["transit_time"],
["asc"]
);
seaFCLJSON.rates.sort = "Faster"; //this is the main culprit
dispatch({ type: SET_SEA_FCL_JSON, payload: seaFCLJSON });
};
to this
//FCL sort by faster
export const sortByFasterFCLJSON = () => async (dispatch, getState) => {
let seaFCLJSON = getState().route.seaFCLJSON;
if (!seaFCLJSON.rates) return;
seaFCLJSON.rates.fcl = _.orderBy(
seaFCLJSON.rates.fcl,
["transit_time"],
["asc"]
);
// seaFCLJSON.rates.sort = "Faster"; //this was the main culprit, got lost
seaFCLJSON = {
...seaFCLJSON,
rates: { ...seaFCLJSON.rates, sort: "Faster" }
};
dispatch({ type: SET_SEA_FCL_JSON, payload: seaFCLJSON });
};
the power of not mutating data
Side note: Redux Troubleshooting
In my react app I have a main App component where I fetched data from api in componentDidMount method and saved it in its state. Then I passed that state to another component in App. However, when I consume that data from prop it is showing undefined.
Another strange this I didn't is when I console.log state in App components render method them first I get an empty array then after a second another array with the data in it. Please help me here
The code goes like this-
class App extends React.Component {
constructor() {
super();
this.state = {
data: []
};
}
componentDidMount() {
this.fetchData();
}
fetchData() {
fetch(
`https://api.themoviedb.org/3/movie/popular?api_key=${
process.env.REACT_APP_API_KEY
}&language=en-US&page=1`
)
.then(res => res.json())
.then(data => {
this.setState({ data });
})
.catch(err => console.log(err));
}
render() {
console.log(this.state.data);
return (
<div>
<Movie title="Popular" results={this.state.data} />
</div>
);
}
}
export default App;
this.state.data is undefined in Movie component which is like this
function Movie(props) {
return (
<p>{props.data.results[0].title}</p>
)
}
You are passing results and title as the props to the <Movie> component yet trying to fetch data prop.
component:
<Movie title="Popular" results={this.state.data} />
So you need to fetch the results prop, not the data one.
fixed:
function Movie(props) {
return (
<p>{props.results[0].title}</p>
)
}
additionaly:
If you're already passing the title prop, why not just use that prop for the title?
function Movie(props) {
return (
<p>{props.title}</p>
)
}
Your prop is results so you need to reference that in your component:
function Movie(props) {
return (
<p>{props.results[0].title}</p>
)
}
In your App component you might also want to add a check in render to show a loading message or spinner if the data load hasn't been resolved when the component initially renders:
if (!this.state.data.length) return <Spinner />;
I'm running into a recurring issue in my code where I want to grab multiple pieces of data from a component to set as states, and push those into an array which is having its own state updated. The way I am doing it currently isn't working and I think it's because I do not understand the order of the way things happen in js and react.
Here's an example of something I'm doing that doesn't work: jsfiddle here or code below.
import React, {Component} from 'react';
class App extends Component {
constructor(props) {
super(props);
this.state = {
categoryTitle: null,
categorySubtitle: null,
categoryArray: [],
}
}
pushToCategoryArray = () => {
this.state.categoryArray.push({
'categoryTitle': this.state.categoryTitle,
'categorySubtitle': this.state.categorySubtitle,
})
}
setCategoryStates = (categoryTitle, categorySubtitle) => {
this.setState({
categoryTitle: categoryTitle,
categorySubtitle: categorySubtitle,
})
this.pushToCategoryArray();
}
render() {
return (
<CategoryComponent
setCategoryStates={this.setCategoryStates}
categoryTitle={'Category Title Text'}
categorySubtitle={'Category Subtitle Text'}
/>
);
}
}
class CategoryComponent extends Component {
render() {
var categoryTitle = this.props.categoryTitle;
var categorySubtitle = this.props.categorySubtitle;
return (
<div onClick={() => (this.props.setCategoryStates(
categoryTitle,
categorySubtitle,
))}
>
<h1>{categoryTitle}</h1>
<h2>{categorySubtitle}</h2>
</div>
);
}
}
I can see in the console that I am grabbing the categoryTitle and categorySubtitle that I want, but they get pushed as null into this.state.categoryArray. Is this a scenario where I need to be using promises? Taking another approach?
This occurs because setState is asynchronous (https://reactjs.org/docs/state-and-lifecycle.html#using-state-correctly).
Here's the problem
//State has categoryTitle as null and categorySubtitle as null.
this.state = {
categoryTitle: null,
categorySubtitle: null,
categoryArray: [],
}
//This gets the correct values in the parameters
setCategoryStates = (categoryTitle, categorySubtitle) => {
//This is correct, you're setting state BUT this is not sync
this.setState({
categoryTitle: categoryTitle,
categorySubtitle: categorySubtitle,
})
this.pushToCategoryArray();
}
//This method is using the state, which as can be seen from the constructor is null and hence you're pushing null into your array.
pushToCategoryArray = () => {
this.state.categoryArray.push({
'categoryTitle': this.state.categoryTitle,
'categorySubtitle': this.state.categorySubtitle,
})
}
Solution to your problem: pass callback to setState
setCategoryStates = (categoryTitle, categorySubtitle) => {
//This is correct, you're setting state BUT this is not sync
this.setState({
categoryTitle: categoryTitle,
categorySubtitle: categorySubtitle,
}, () => {
/*
Add state to the array
This callback will be called once the async state update has succeeded
So accessing state in this variable will be correct.
*/
this.pushToCategoryArray()
})
}
and change
pushToCategoryArray = () => {
//You don't need state, you can simply make these regular JavaScript variables
this.categoryArray.push({
'categoryTitle': this.state.categoryTitle,
'categorySubtitle': this.state.categorySubtitle,
})
}
I think React doesn't re-render because of the pushToCategoryArray that directly change state. Need to assign new array in this.setState function.
// this.state.categoryArray.push({...})
const prevCategoryArray = this.state.categoryArray
this.setState({
categoryArray: [ newObject, ...prevCategoryArray],
)}
In my componentDidMount(), I am calling an actionCreator in my redux file to do an API call to get a list of items. This list of items is then added into the redux store which I can access from my component via mapStateToProps.
const mapStateToProps = state => {
return {
list: state.list
};
};
So in my render(), I have:
render() {
const { list } = this.props;
}
Now, when the page loads, I need to run a function that needs to map over this list.
Let's say I have this method:
someFunction(list) {
// A function that makes use of list
}
But where do I call it? I must call it when the list is already available to me as my function will give me an error the list is undefined (if it's not yet available).
I also cannot invoke it in render (before the return statement) as it gives me an error that render() must be pure.
Is there another lifecycle method that I can use?
Just do this, and in redux store please make sure that initial state of list should be []
const mapStateToProps = state => {
return {
list: someFunction(state.list)
};
};
These are two ways you can play with received props from Redux
Do it in render
render() {
const { list } = this.props;
const items = list && list.map((item, index) => {
return <li key={item.id}>{item.value}</li>
});
return(
<div>
{items}
</div>
);
}
Or Do it in componentWillReceiveProps method if you are not using react 16.3 or greater
this.state = {
items: []
}
componentWillReceiveProps(nextProps){
if(nextProps.list != this.props.list){
const items = nextProps.list && nextProps.list.map((item, index) => {
return <li key={item.id}>{item.value}</li>
});
this.setState({items: items});
}
}
render() {
const {items} = this.state;
return(
<div>
{items}
</div>
);
}
You can also do it in componentDidMount if your Api call is placed in componentWillMount or receiving props from parent.
I am having trouble creating an array of titles from an Axios response. The method getTitles(props) receives data from the Axios response. How do I create an array of titles dynamically?
The functions I have tried in Javascript are for loops and EC6 mapping, nothing seems to work. Being new to react I could be missing something but I am not sure what it is.
React code
export default class Featured extends React.Component {
constructor() {
super();
this.state = {
data: null,
}
}
/**
* Received request from server
*/
componentDidMount(){
ApiCalls.articleData()
.then(function(data){
this.setState(function(){
return {
data: data
}
})
}.bind(this));
}
getTitles(props){
//-- What code do I place here?
console.log(props.data)
return ['test title', 'test title 2'];
}
/**
* Render request
*/
render() {
let dataResponse = JSON.stringify(this.state.data, null, 2);
const Articles = this.getTitles(this.state).map((title, i) => <Article key={i} title={title}/> );
return (
<div class="row">{Articles}
<pre>{dataResponse}</pre>
</div>
);
}
}
Axios Code
var ApiCalls = {
articleData: function(id){
return axios.all([getArticles(id)])
.then(function(arr){
return arr[0].data.data;
})
.catch(function (error) {
console.log(error);
})
},
React setState behaves asynchronously . Your articles get rendered before the ajax was called and was not re rendered due to asynchrony in setState.
This is what doc(https://reactjs.org/docs/react-component.html#setstate) says
setState() does not always immediately update the component. It may batch or defer the update until later. This makes reading this.state right after calling setState() a potential pitfall. Instead, use componentDidUpdate or a setState callback (setState(updater, callback)), either of which are guaranteed to fire after the update has been applied. If you need to set the state based on the previous state, read about the updater argument below.
You can render the article after successful ajax call like below
componentDidMount(){
ApiCalls.articleData()
.then(function(data){
render(<Article data={data}/>, document.getElementById('...'));
}.bind(this));
}
Because of the post above, I was able to fix the issue by the code example below To see a working example goto the git repo
ApiCalls.articleData()
.then(function(data){
const newData = data.map(c => {
return c.attributes.title;
})
const addElement = newData.map((title, i) => <ContentTiles key={i} title={title}/> );
const newState = Object.assign({}, this.state, {
newData: addElement
});
this.setState(newState);
}.bind(this));