My code adds a new item in the firebase databse when i click a button, then i want the list of objects in my page to automatically update, because i don't want to manualy reload the page. So i came up with this code
constructor(props){
super(props);
this.state = {
groups: [],
code:'',
name:'',
update:true
}
}
async fetchGroups (id){
fetchGroupsFirebase(id).then((res) => {this.setState({groups:res})})
};
async componentDidUpdate(prevProps,prevState){
if(this.state.update !== prevState.update){
await this.fetchGroups(this.props.user.id);
}
}
handleCreateSubmit = async event => {
event.preventDefault();
const{name} = this.state;
try{
firestore.collection("groups").add({
title:name,
owner:this.props.user.id
})
.then((ref) => {
firestore.collection("user-group").add({
idGroup:ref.id,
idUser:this.props.user.id
});
});
this.setState({update: !this.state.update});
}catch(error){
console.error(error);
}
What i was thinking, after i add the new item in firebase, i change the state.update variable, which triggers componentDidUpdate, which calls the new fetching.
I tried calling the fetchGroups function in the submit function, but that didn't work either.
What am i doing wrong and how could i fix it?
ComponentDidUpdate will not be called on initial render. You can either additionally use componentDidMount or replace the class component with a functional component and use the hook useEffect instead.
Regarding useEffect, this could be your effect:
useEffect(() => {
await this.fetchGroups(this.props.user.id);
}, [update]);
Since you can't use useEffect in class components so you would need to rewrite it as functional and replace your this.state with useState.
Related
Here is the code I used in the function component
useEffect(() => {
const unsubscribe = firebase.auth().onAuthStateChanged(user => {
setIsLoggedIn(!!user);
});
return () => {
unsubscribe();
};
});
Here is my try on the class component.
componentDidUpdate(
prevProps: LessonDrawerProps,
prevState: LessonDrawerState
) {
firebase.auth().onAuthStateChanged(user => {
if (user) {
this.setState({
isLoggedIn: true,
});
}
});
}
The class onAuthStateChanged detection is not working properly as in the function component.
How can this be done?
The componentDidUpdate fires when the component was updated, which in your case seems to never happen (or at least not in time). You actually want to start listening for auth state changes as soon as the component is added to the widget tree.
You'll want to put the onAutStateChanged in the componentDidMount instead of in componentDidUpdate.
In my react app I have component named profile, and I am fetching data from server and showing it inside that component. I am using redux and redux-thunk along with axios. With help of mapDispatchToProps function, i am calling redux action for fetching that data when component is mounted and saving it to redux state. After that, using mapStateToProps function i am showing that data on the screen via props. That works fine. Now I want to have possibility to edit, for example, first name of that user. To accomplish that i need to save that data to component state when data is fetched from server, and then when text field is changed, component state also needs to be changed. Don't know how to save data to component sate, immediately after it is fetched.
Simplified code:
const mapStateToProps = (state) => {
return {
user: state.user
}
}
const mapDispatchToProps = (dispatch) => {
return {
getUserData: () => dispatch(userActions.getUserData())
}
}
class Profile extends Component {
state:{
user: {}
}
componentDidMount (){
this.props.getUserData()
// when data is saved to redux state i need to save it to component state
}
editTextField = () => {
this.setState({
[e.target.id]: e.target.value
})
};
render(){
const { user } = this.props;
return(
<TextField id="firstName"
value={user.firstName}
onChange={this.editTextField}
/>
)
}
}
You can use componentDidUpdate for that or give a callback function to your action.
I will show both.
First lets see componentDidUpdate,
Here you can compare your previous data and your present data, and if there is some change, you can set your state, for example if you data is an array.
state = {
data: []
}
then inside your componentDidUpdate
componentDidUpdate(prevProps, prevState) {
if(prevProps.data.length !== this.props.data.length) {
// update your state, in your case you just need userData, so you
// can compare something like name or something else, but still
// for better equality check, you can use lodash, it will also check for objects,
this.setState({ data: this.props.data});
}
}
_.isEqual(a, b); // returns false if different
This was one solution, another solution is to pass a call back funtion to your action,
lets say you call this.props.getData()
you can do something like this
this.props.getData((data) => {
this.setState({ data });
})
here you pass your data from redux action to your state.
your redux action would be something like this.
export const getData = (done) => async dispatch => {
const data = await getSomeData(); // or api call
// when you dispatch your action, also call your done
done(data);
}
If you are using React 16.0+, you can use the static method getDerivedStateFromProps. You can read about it react docs.
Using your example:
class Profile extends Component {
// other methods here ...
static getDerivedStateFromProps(props) {
return {
user: props.user
}
}
// other methods here...
}
I am getting the data from my form component and trying to set the state of my app component with this data.
However, the state.data is an empty object and is not updating the data. I console log the model data before setting it to check if it exists. Their is data within the model.
import React, { Component, Fragment } from "react";
import Form from "../components/Form";
import product from "./product.json";
class App extends Component {
constructor() {
super();
this.state = {
data: {}
};
}
onSubmit = (model) => {
console.log("Outer", model);
this.setState({
data: model
});
console.log("Form: ", this.state);
}
render() {
const fields = product.fields;
return (
<Fragment>
<div>Header</div>
<Form
model={fields}
onSubmit={(model) => {this.onSubmit(model);}}
/>
<div>Footer</div>
</Fragment>
);
}
}
export default App;
setState() is an async call in React. So you won't likely get the updated state value in the next line. To check the updated value on successful state update, you could check in the callback handler.
Change this
onSubmit = (model) => {
console.log("Outer", model);
this.setState({
data: model
});
console.log("Form: ", this.state);
}
to
onSubmit = (model) => {
console.log("Outer", model);
this.setState({
data: model
}, () => {
console.log("Form: ", this.state);
});
}
As per the react docs, setState is an asynchronous call. You can ensure your state has updated to perform a particular action in two ways as shown below:
You can pass the setState a function which will have your current state and props and you the value you return will be your next state of the component.
Keep in mind following:
state is a reference to the component state at the time the change is
being applied. It should not be directly mutated. Instead, changes
should be represented by building a new object based on the input from
state and props.
Following is an example:
this.setState((state, props) => {
//do something
return {counter: state.counter + props.step};
});
You can pass a callback to the setState function as mentioned in Dinesh's
answer. The callback will be executed once the state has been updated successfully hence ensuring you will have the updated state in the call back.
Following is an example:
this.setState({ ...new state }, () => {
// do something
});
Hope it helps.
I just want to add, that if you will do like this its not going to work:
this.setState({things} , console.log(this.state))
You have to pass a refarence to the call back and not the exscutable code itself. If you won't do so, the function will envoke before the state is updated,even you will see the log.
I have managed to fetch data from an API successfully. Data transformation of JSON format works too, but i'm having trouble integrating it to "componentDidMount" to set state with a transformed JSON format. I'm getting an undefined state when i console.log(this.state.races).
I'm also getting this error message:
Can't call setState (or forceUpdate) on an unmounted component.
class Races extends Component {
constructor(props) {
super(props);
this.state = {
races: []};
this.processResults = this.processResults.bind(this);
}
componentDidMount(){
fetch(RACE_SERVICE_URL)
.then(results => results.json())
.then(this.processResults)
}
processResults(data) {
const raceId_arr = data.map(d => d.raceId);
const season_arr = data.map(d => d.season);
const raceName_arr = data.map(d => d.raceName);
const url_arr = data.map(d => d.url);
const data_mapped = {'raceId': raceId_arr, 'season': season_arr, 'raceName': raceName_arr, 'url': url_arr};
this.setState({races:data_mapped});
console.log(data_mapped);
console.log(this.state.races);
}
render() {
const title = 'Race Tracks';
return (
<div>
<h2>{title}</h2>
<RacesViz data= {this.state.races.raceId} />
</div>
);
}
}
export default Races;
I have also tried:
.then(data => this.processResults(data))
What console.log(data_mapped) prints:
{raceId:[1, 2, 3]
raceName:["AGP", "BGP", "CGP"]
season: [2018, 2018, 2018]
url: ["http://en.wikipedia.org/wiki/AGP", "http://en.wikipedia.org/wiki/BGP", "http://en.wikipedia.org/wiki/CGP"]}
setState is async so you can't get immediate result with console.log like you did. Use a callback function instead:
this.setState({races:data_mapped}, () => console.log(this.state.races));
Or you can console.log your state in your render method.
Quote from official docs:
Think of setState() as a request rather than an immediate command to update the component. For better perceived performance, React may delay it, and then update several components in a single pass. React does not guarantee that the state changes are applied immediately.
Important!
This makes reading this.state right after calling setState() a potential pitfall.
So you will not get state immediately after setState. You have 2 ways to solve it.
1) You should check in componentDidUpdate hook.
componentDidUpdate(prevProps, prevState) {
console.log(this.state.races);//your data updated here.
}
You can see here to use properly.
2) Or you use callback in setState like this setState(updater, callback):
this.setState({races:data_mapped}, () => {
console.log(this.state.races)//your data updated here.
})
I'm new to Mobx and reactjs in general, I have knowledge in Redux and react native, and in Redux when I used to call an action and the props get updated, the componentDidUpdate life cycle method is triggered.
The scenario I'm having now is login. so the user fills the form, clicks submit, and the submit calls a Mobx action (asynchronous), and when the server responds, an observable is updated, and then it navigates to a main page (navigation happens in the component).
Here is my store code.
import { autorun, observable, action, runInAction, computed, useStrict } from 'mobx';
useStrict(true);
class LoginStore {
#observable authenticated = false;
#observable token = '';
#computed get isAuthenticated() { return this.authenticated; }
#action login = async (credentials) => {
const res = await window.swaggerClient.Auth.login(credentials)l
// checking response for erros
runInAction(() => {
this.token = res.obj.token;
this.authenticated = true;
});
}
}
const store = new LoginStore();
export default store;
export { LoginStore };
and this handler is in my component.
handleSubmit = (e) => {
e.preventDefault();
this.props.form.validateFields((err, values) => {
if (!err) {
this.props.store.login(values);
}
});
}
componentDidUpdate() {
if (this.props.store.isAuthenticated) {
const cookies = new Cookies();
cookies.set('_cookie_name', this.props.store.token);
this.props.history.push('main');
}
}
It's not the ideal code, I'm just experimenting, but I'm not quite getting it.
Also, if I use the computed value (isAuthenticated) in the render life cycle method, the componentDidUpdate is triggered, but if I didn't use it in the render method, the componentDidUpdate is not triggered.
For example, if I do this
render() {
if (this.props.store.isAuthenticated) return null
// .... rest of the code here
}
the above will trigger the componentDidUpdate.
Am I missing something? is there a better way to do it with Mobx?
Thanks
Observer component will only react to observables referred in its render method. MobX documentation covers this.
I would recommend you to use when to solve the problem.
componentDidMount() {
when(
() => this.props.store.isAuthenticated,
() => {
// put your navigation logic here
}
);
}
Mobx suggest the following solutions for such a case:
when
autorun
reaction
See the examples below, and don't forget to dispose:
componentDidMount() {
this.disposers.push(
// option with autorun:
autorun(() => {
this.runYourLogicHere();
})
// another option with reaction:
reaction(
() => this.yourModelOrProps.something,
() => {
this.runYourLogicHere();
}
)
)
}
...
componentWillUnmount() {
this.disposers.forEach(disposer => {
disposer();
});
}
And see the answer of #Dominik Serafin in parallel thread as a reference.