I'm having an issue where I want to save the data from a particular fieldset with the default values on componentDidMount().
The data saving happens in the parent component, after it is sent up from the child component. However, as React's setState() is asynchronous, it is only saving data from one of the fields. I have outlined a skeleton version of my problem below. Any ideas how I can fix this?
// Parent Component
class Form extends Component {
super(props);
this.manageData = this.manageData.bind(this);
this.state = {
formData: {}
}
}
manageData(data) {
var newObj = {
[data.name]: data.value
}
var currentState = this.state.formData;
var newState = Object.assign({}, currentState, newObj);
this.setState({
formData: newState, // This only sets ONE of the fields from ChildComponent because React delays the setting of state.
)};
render() {
return (
<ChildComponent formValidate={this.manageData} />
)
}
// Child Component
class ChildComponent extends Component {
componentDidMount() {
const fieldA = {
name: 'Phone Number',
value: '123456678'
},
fieldB = {
name: 'Email Address',
value: 'john#example.com'
}
this.props.formValidate(fieldA);
this.props.formValidate(fieldB)
}
render() {
/// Things happen here.
}
}
You're already answering you're own question. React handles state asynchronously and as such you need to make sure you use the current component's state when setState is invoked. Thankfully the team behind React is well-aware of this and have provided an overload for the setState method. I would modify your manageData call to the following:
manageData(data) {
this.setState(prevState => {
const nextState = Object.assign({}, prevState);
nextState.formData[data.name] = data.value;
return nextState;
});
}
This overload for the setState takes a function whose first parameter is the component's current state at the time that the setState method is invoked. Here is the link where they begin discussing this form of the setState method.
https://reactjs.org/docs/state-and-lifecycle.html#state-updates-may-be-asynchronous
Change manageData to this
manageData(data) {
const newObj = {
[data.name]: data.value
};
this.setState(prevState => ({
formData: {
...prevState.formData,
...newObj
}
}));
}
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
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],
)}
I'm building web app in React with Redux. It is simple device manager. I'm using the same component for adding and updating device in database. I'm not sure, if my approach is correct. Here you can find parts of my solution:
UPDATE MODE:
In componentDidMount I'm checking, if deviceId was passed in url (edit mode). If so, I'm calling redux action to get retrieve data from database. I'm using connect function, so when response arrives, It will be mapped to component props.
Here is my mapStateToProps (probably I should map only specific property but it does not matter in this case)
const mapStateToProps = state => ({
...state
})
and componentDidMount:
componentDidMount() {
const deviceId = this.props.match.params.deviceId;
if (deviceId) {
this.props.getDevice(deviceId);
this.setState({ editMode: true });
}
}
Next, componentWillReceiveProps will be fired and I will be able to call setState in order to populate inputs in my form.
componentWillReceiveProps(nextProps) {
if (nextProps.devices.item) {
this.setState({
id: nextProps.devices.item.id,
name: nextProps.devices.item.name,
description: nextProps.devices.item.description
});
}
}
ADD MODE:
Add mode is even simpler - I'm just calling setState on each input change.
handleChange = name => event => {
this.setState({
[name]: event.target.value,
});
};
That's how my inputs looks:
<TextField
onChange={this.handleChange('description')}
label="Description"
className={classes.textField}
value={this.state.description}
/>
I don't like this approach because I have to call setState() after receiving data from backend. I'm also using componentWillReceiveProps which is bad practice.
Are there any better approaches? I can use for example only redux store instead of component state (but I don't need inputs data in redux store). Maybe I can use React ref field and get rid of component state?
Additional question - should I really call setState on each input onChange?
To avoid using componentWillReceiveProps, and because you are using redux, you can do:
class YourComponent extends React.Component {
state = {
// ...
description: undefined,
};
static getDerivedStateFromProps(nextProps, prevState) {
if (prevState.description === undefined && nextProps.description) {
return { description: nextProps.description };
}
return null;
}
componentDidMount() {
const deviceId = this.props.match.params.deviceId;
if (deviceId) {
this.props.getDevice(deviceId);
this.setState({ editMode: true });
}
}
handleChange = name => event => {
this.setState({
[name]: event.target.value,
});
};
// ...
render() {
let { description } = this.state;
description = description || ''; // use this value in your `TextField`.
// ...
return (
<TextField
onChange={this.handleChange('description')}
label="Description"
className={classes.textField}
value={description}
/>
);
}
}
const mapStateToProps = (state) => {
let props = { ...state };
const { devices } = state;
if (devices && devices.item) {
props = {
...props,
id: devices.item.id,
name: devices.item.name,
description: devices.item.description,
};
}
return props;
};
export default connect(
mapStateToProps,
)(YourComponent);
You can then access id, name, and description thought this.props instead of this.state. It works because mapStateToProps will be evaluated every time you update the redux store. Also, you will be able to access description through this.state and leave your TextField as is. You can read more about getDerivedStateFromProps here.
As for your second question, calling setState every time the input changes is totally fine; that's what's called a controlled component, and the react team (nor me) encourage its use. See here.
This question already has answers here:
Reactjs - Setting State from props using setState in child component
(2 answers)
Closed 5 years ago.
So as I understand, a component will re-render when there has been a change in props and componentWillMount shall run before re-rendering. At the moment my constructor and componentWillMount run as expected, but then the question prop changes which I need to update the user score state, but this change in question prop doesn't trigger the constructor or componentWillMount. As I shouldn't update the state inside the render function (the only place so far that I have been able to get access to the updated question prop), how can I make react recognise this change in it's props and then update the state? Hope that's understandable.
Here is my container
class FullTimeScoreContainer extends Component<Props, State> {
constructor(props: Props) {
super(props)
this.state = {
userHomeScore: 1,
userAwayScore: 1
}
}
componentWillMount() {
getFTSAnswerStatus(this.props.question).then(foundScores => {
if ( foundScores.userHomeScore ) {
this.setState({
userHomeScore: foundScores.userHomeScore,
userAwayScore: foundScores.userAwayScore
});
}
})
}
render() {
const { option, question, questionIndex, user, configs, renderAs, showNextQuestionAfterFTS, total} = this.props;
// check if question is active or not
let ComponentClass;
if ( question[0].active ) {
ComponentClass = FullTimeScoreActive;
} else {
ComponentClass = FullTimeScoreLocked;
}
const changeScoreState = (team, val) => {
switch (team) {
case "home":
this.setState( (prevState) => ({ userHomeScore: prevState.userHomeScore + val }) );
break;
case "away":
this.setState( (prevState) => ({ userAwayScore: prevState.userAwayScore + val }) );
break;
default:
throw new Error("unrecognised team to change score state")
}
}
const onClickCallback = () => {
const p = this.props;
const s = this.state;
p.showNextQuestionAfterFTS();
p.recordFullTimeScoreAnswer(s.userHomeScore, s.userAwayScore, p.question, p.questionIndex, p.user, p.configs)
}
return (
<ComponentClass
imgSrc={imgSrc}
user={user}
answerStatus={answerStatus}
question={question}
onClickCallback={onClickCallback}
questionIndex={questionIndex}
total={total}
configs={configs}
userScores={this.state}
changeScoreState={changeScoreState}
/>
)
}
}
const mapStateToProps = state => {
return {
configs: state.configs,
user: state.user
};
}
function mapDispatchToProps(dispatch) {
return bindActionCreators({ recordFullTimeScoreAnswer, showNextQuestionAfterFTS }, dispatch);
};
export default connect(mapStateToProps, mapDispatchToProps)(FullTimeScoreContainer);
export { FullTimeScoreContainer }
componentWillMount will only run before the first render. It doesn't get run before every render. So even if your state and props update, componentWillMount will not get called again.
The constructor function is the same as well.
You might be looking for componentWillReceiveProps (see docs). This lifecycle event is called when a mounted component is about to receive new props. You can update your state in this lifecycle event.
Note that componentWillReceiveProps only works on mounted components. Therefore, it will not get called the first time your component receives its' initial props.
A side note: Per the docs, you also don't want to introduce any side-effects or subscriptions in componentWillMount. Do that in componentDidMount instead.
I would like add a comment, but I don't have enough reputation...
a component will re-render when there has been a change in props
As I understand, you can't change the props, so component re-render on state changes.
I need to get data from DB depending on a search string value. Therefore I'm using an input field. The search string is stored as a state value.
The data for the component comes from a container (using npm meteor/react-meteor-data).
Now my problem is, how do I get the search string into the container to set the parameter for the publication?
container/example.js
export default createContainer((prop) => {
Meteor.subscribe('images', searchString) // How to get searchString?
return { files: Images.find({}).fetch() }
}, Example)
component/example.jsx
class Example extends Component {
constructor(props) {
super(props)
this.state = {
searchString: ''
}
}
searchImage(event) {
const searchString = event.target.value
this.setState({ searchString })
}
render() {
return (<Input onChange={ this.searchImage.bind(this) }/>)
}
}
export default Example
publication
Meteor.publish('images', function(search) {
return Images.find({ title: search }).cursor
})
Maybe you can create two different components: a parent and a child, and you can wrap child component with createContainer HOC like the following
childComponent.js
const Example = (props) => {
return <Input onChange={props.searchImage}/>
}
export default createContainer(({searchString}) => {
Meteor.subscribe('images', searchString)
return { files: Images.find({}).fetch() }
}, Example)
parentComponent.js
class ExampleWrapper extends Component {
constructor(props) {
super(props)
this.state = {
searchString: ''
}
}
searchImage = (event) => {
const searchString = event.target.value
this.setState({ searchString })
} // instead of binding this, you can also use arrow function that
// takes care of binding
render() {
return (<Example searchImage={this.searchImage} searchString={this.state.searchString} {...this.props} />)
}
}
export default ExampleWrapper
The idea is, since createContainer is a higher order component, it doesn't have access to the props of any component wrapped by it.
What we need to do is, passing the value of searchString from a parent component.
The way to do is the following:
ExampleWrapper has a state called searchString and Example component has a prop called searchString. We can set the value of searchString prop to state.searchString.
Since the default export corresponds to createContainer({..some logic…}, Example}), createContainer can make use of prop called searchString.
In order to change the value of state.searchString we also passed searchImage function as a prop to Example component. Whenever there is a change event, onChange triggers searchImage function that updates the value of state.searchString. And eventually, the minute the value of state.searchString changes searchString prop’s value changes thus your subscription result also changes
onChange={ (e)=> {this.setState({ searchString: $(e.target).val() }) } }
This is how we assign values to our internal state properties :)
EDIT: I appear to have misunderstood the question...