I am trying to learn hooks and the useState method has made me confused. I am assigning an initial value to a state in the form of an array. The set method in useState is not working for me, both with and without the spread syntax.
I have made an API on another PC that I am calling and fetching the data which I want to set into the state.
Here is my code:
<div id="root"></div>
<script type="text/babel" defer>
// import React, { useState, useEffect } from "react";
// import ReactDOM from "react-dom";
const { useState, useEffect } = React; // web-browser variant
const StateSelector = () => {
const initialValue = [
{
category: "",
photo: "",
description: "",
id: 0,
name: "",
rating: 0
}
];
const [movies, setMovies] = useState(initialValue);
useEffect(() => {
(async function() {
try {
// const response = await fetch("http://192.168.1.164:5000/movies/display");
// const json = await response.json();
// const result = json.data.result;
const result = [
{
category: "cat1",
description: "desc1",
id: "1546514491119",
name: "randomname2",
photo: null,
rating: "3"
},
{
category: "cat2",
description: "desc1",
id: "1546837819818",
name: "randomname1",
rating: "5"
}
];
console.log("result =", result);
setMovies(result);
console.log("movies =", movies);
} catch (e) {
console.error(e);
}
})();
}, []);
return <p>hello</p>;
};
const rootElement = document.getElementById("root");
ReactDOM.render(<StateSelector />, rootElement);
</script>
<script src="https://unpkg.com/#babel/standalone#7/babel.min.js"></script>
<script src="https://unpkg.com/react#17/umd/react.production.min.js"></script>
<script src="https://unpkg.com/react-dom#17/umd/react-dom.production.min.js"></script>
Neither setMovies(result) nor setMovies(...result) works.
I expect the result variable to be pushed into the movies array.
Much like .setState() in class components created by extending React.Component or React.PureComponent, the state update using the updater provided by useState hook is also asynchronous, and will not be reflected immediately.
Also, the main issue here is not just the asynchronous nature but the fact that state values are used by functions based on their current closures, and state updates will reflect in the next re-render by which the existing closures are not affected, but new ones are created. Now in the current state, the values within hooks are obtained by existing closures, and when a re-render happens, the closures are updated based on whether the function is recreated again or not.
Even if you add a setTimeout the function, though the timeout will run after some time by which the re-render would have happened, the setTimeout will still use the value from its previous closure and not the updated one.
setMovies(result);
console.log(movies) // movies here will not be updated
If you want to perform an action on state update, you need to use the useEffect hook, much like using componentDidUpdate in class components since the setter returned by useState doesn't have a callback pattern
useEffect(() => {
// action on update of movies
}, [movies]);
As far as the syntax to update state is concerned, setMovies(result) will replace the previous movies value in the state with those available from the async request.
However, if you want to merge the response with the previously existing values, you must use the callback syntax of state updation along with the correct use of spread syntax like
setMovies(prevMovies => ([...prevMovies, ...result]));
Additional details to the previous answer:
While React's setState is asynchronous (both classes and hooks), and it's tempting to use that fact to explain the observed behavior, it is not the reason why it happens.
TLDR: The reason is a closure scope around an immutable const value.
Solutions:
read the value in render function (not inside nested functions):
useEffect(() => { setMovies(result) }, [])
console.log(movies)
add the variable into dependencies (and use the react-hooks/exhaustive-deps eslint rule):
useEffect(() => { setMovies(result) }, [])
useEffect(() => { console.log(movies) }, [movies])
use a temporary variable:
useEffect(() => {
const newMovies = result
console.log(newMovies)
setMovies(newMovies)
}, [])
use a mutable reference (if we don't need a state and only want to remember the value - updating a ref doesn't trigger re-render):
const moviesRef = useRef(initialValue)
useEffect(() => {
moviesRef.current = result
console.log(moviesRef.current)
}, [])
Explanation why it happens:
If async was the only reason, it would be possible to await setState().
However, both props and state are assumed to be unchanging during 1 render.
Treat this.state as if it were immutable.
With hooks, this assumption is enhanced by using constant values with the const keyword:
const [state, setState] = useState('initial')
The value might be different between 2 renders, but remains a constant inside the render itself and inside any closures (functions that live longer even after render is finished, e.g. useEffect, event handlers, inside any Promise or setTimeout).
Consider following fake, but synchronous, React-like implementation:
// sync implementation:
let internalState
let renderAgain
const setState = (updateFn) => {
internalState = updateFn(internalState)
renderAgain()
}
const useState = (defaultState) => {
if (!internalState) {
internalState = defaultState
}
return [internalState, setState]
}
const render = (component, node) => {
const {html, handleClick} = component()
node.innerHTML = html
renderAgain = () => render(component, node)
return handleClick
}
// test:
const MyComponent = () => {
const [x, setX] = useState(1)
console.log('in render:', x) // ✅
const handleClick = () => {
setX(current => current + 1)
console.log('in handler/effect/Promise/setTimeout:', x) // ❌ NOT updated
}
return {
html: `<button>${x}</button>`,
handleClick
}
}
const triggerClick = render(MyComponent, document.getElementById('root'))
triggerClick()
triggerClick()
triggerClick()
<div id="root"></div>
I know that there are already very good answers. But I want to give another idea how to solve the same issue, and access the latest 'movie' state, using my module react-useStateRef.
As you understand by using React state you can render the page every time the state change. But by using React ref, you can always get the latest values.
So the module react-useStateRef let you use state's and ref's together. It's backward compatible with React.useState, so you can just replace the import statement
const { useEffect } = React
import { useState } from 'react-usestateref'
const [movies, setMovies] = useState(initialValue);
useEffect(() => {
(async function() {
try {
const result = [
{
id: "1546514491119",
},
];
console.log("result =", result);
setMovies(result);
console.log("movies =", movies.current); // will give you the latest results
} catch (e) {
console.error(e);
}
})();
}, []);
More information:
react-usestsateref
I just finished a rewrite with useReducer, following #kentcdobs article (ref below) which really gave me a solid result that suffers not one bit from these closure problems.
See: https://kentcdodds.com/blog/how-to-use-react-context-effectively
I condensed his readable boilerplate to my preferred level of DRYness -- reading his sandbox implementation will show you how it actually works.
import React from 'react'
// ref: https://kentcdodds.com/blog/how-to-use-react-context-effectively
const ApplicationDispatch = React.createContext()
const ApplicationContext = React.createContext()
function stateReducer(state, action) {
if (state.hasOwnProperty(action.type)) {
return { ...state, [action.type]: state[action.type] = action.newValue };
}
throw new Error(`Unhandled action type: ${action.type}`);
}
const initialState = {
keyCode: '',
testCode: '',
testMode: false,
phoneNumber: '',
resultCode: null,
mobileInfo: '',
configName: '',
appConfig: {},
};
function DispatchProvider({ children }) {
const [state, dispatch] = React.useReducer(stateReducer, initialState);
return (
<ApplicationDispatch.Provider value={dispatch}>
<ApplicationContext.Provider value={state}>
{children}
</ApplicationContext.Provider>
</ApplicationDispatch.Provider>
)
}
function useDispatchable(stateName) {
const context = React.useContext(ApplicationContext);
const dispatch = React.useContext(ApplicationDispatch);
return [context[stateName], newValue => dispatch({ type: stateName, newValue })];
}
function useKeyCode() { return useDispatchable('keyCode'); }
function useTestCode() { return useDispatchable('testCode'); }
function useTestMode() { return useDispatchable('testMode'); }
function usePhoneNumber() { return useDispatchable('phoneNumber'); }
function useResultCode() { return useDispatchable('resultCode'); }
function useMobileInfo() { return useDispatchable('mobileInfo'); }
function useConfigName() { return useDispatchable('configName'); }
function useAppConfig() { return useDispatchable('appConfig'); }
export {
DispatchProvider,
useKeyCode,
useTestCode,
useTestMode,
usePhoneNumber,
useResultCode,
useMobileInfo,
useConfigName,
useAppConfig,
}
With a usage similar to this:
import { useHistory } from "react-router-dom";
// https://react-bootstrap.github.io/components/alerts
import { Container, Row } from 'react-bootstrap';
import { useAppConfig, useKeyCode, usePhoneNumber } from '../../ApplicationDispatchProvider';
import { ControlSet } from '../../components/control-set';
import { keypadClass } from '../../utils/style-utils';
import { MaskedEntry } from '../../components/masked-entry';
import { Messaging } from '../../components/messaging';
import { SimpleKeypad, HandleKeyPress, ALT_ID } from '../../components/simple-keypad';
export const AltIdPage = () => {
const history = useHistory();
const [keyCode, setKeyCode] = useKeyCode();
const [phoneNumber, setPhoneNumber] = usePhoneNumber();
const [appConfig, setAppConfig] = useAppConfig();
const keyPressed = btn => {
const maxLen = appConfig.phoneNumberEntry.entryLen;
const newValue = HandleKeyPress(btn, phoneNumber).slice(0, maxLen);
setPhoneNumber(newValue);
}
const doSubmit = () => {
history.push('s');
}
const disableBtns = phoneNumber.length < appConfig.phoneNumberEntry.entryLen;
return (
<Container fluid className="text-center">
<Row>
<Messaging {...{ msgColors: appConfig.pageColors, msgLines: appConfig.entryMsgs.altIdMsgs }} />
</Row>
<Row>
<MaskedEntry {...{ ...appConfig.phoneNumberEntry, entryColors: appConfig.pageColors, entryLine: phoneNumber }} />
</Row>
<Row>
<SimpleKeypad {...{ keyboardName: ALT_ID, themeName: appConfig.keyTheme, keyPressed, styleClass: keypadClass }} />
</Row>
<Row>
<ControlSet {...{ btnColors: appConfig.buttonColors, disabled: disableBtns, btns: [{ text: 'Submit', click: doSubmit }] }} />
</Row>
</Container>
);
};
AltIdPage.propTypes = {};
Now everything persists smoothly everywhere across all my pages
React's useEffect has its own state/lifecycle. It's related to mutation of state, and it will not update the state until the effect is destroyed.
Just pass a single argument in parameters state or leave it a black array and it will work perfectly.
React.useEffect(() => {
console.log("effect");
(async () => {
try {
let result = await fetch("/query/countries");
const res = await result.json();
let result1 = await fetch("/query/projects");
const res1 = await result1.json();
let result11 = await fetch("/query/regions");
const res11 = await result11.json();
setData({
countries: res,
projects: res1,
regions: res11
});
} catch {}
})(data)
}, [setData])
# or use this
useEffect(() => {
(async () => {
try {
await Promise.all([
fetch("/query/countries").then((response) => response.json()),
fetch("/query/projects").then((response) => response.json()),
fetch("/query/regions").then((response) => response.json())
]).then(([country, project, region]) => {
// console.log(country, project, region);
setData({
countries: country,
projects: project,
regions: region
});
})
} catch {
console.log("data fetch error")
}
})()
}, [setData]);
Alternatively, you can try React.useRef() for instant change in the React hook.
const movies = React.useRef(null);
useEffect(() => {
movies.current='values';
console.log(movies.current)
}, [])
The closure is not the only reason.
Based on the source code of useState (simplified below). Seems to me the value is never assigned right away.
What happens is that an update action is queued when you invoke setValue. And after the schedule kicks in and only when you get to the next render, these update action then is applied to that state.
Which means even we don't have closure issue, react version of useState is not going to give you the new value right away. The new value doesn't even exist until next render.
function useState(initialState) {
let hook;
...
let baseState = hook.memoizedState;
if (hook.queue.pending) {
let firstUpdate = hook.queue.pending.next;
do {
const action = firstUpdate.action;
baseState = action(baseState); // setValue HERE
firstUpdate = firstUpdate.next;
} while (firstUpdate !== hook.queue.pending);
hook.queue.pending = null;
}
hook.memoizedState = baseState;
return [baseState, dispatchAction.bind(null, hook.queue)];
}
function dispatchAction(queue, action) {
const update = {
action,
next: null
};
if (queue.pending === null) {
update.next = update;
} else {
update.next = queue.pending.next;
queue.pending.next = update;
}
queue.pending = update;
isMount = false;
workInProgressHook = fiber.memoizedState;
schedule();
}
There's also an article explaining the above in the similar way, https://dev.to/adamklein/we-don-t-know-how-react-state-hook-works-1lp8
I too was stuck with the same problem. As other answers above have clarified the error here, which is that useState is asynchronous and you are trying to use the value just after setState. It is not updating on the console.log() part because of the asynchronous nature of setState, it lets your further code to execute, while the value updating happens on the background. Thus you are getting the previous value. When the setState is completed on the background it will update the value and you will have access to that value on the next render.
If anyone is interested to understand this in detail. Here is a really good Conference talk on the topic.
https://www.youtube.com/watch?v=8aGhZQkoFbQ
I found this to be good. Instead of defining state (approach 1) as, example,
const initialValue = 1;
const [state,setState] = useState(initialValue)
Try this approach (approach 2),
const [state = initialValue,setState] = useState()
This resolved the rerender issue without using useEffect since we are not concerned with its internal closure approach with this case.
P.S.: If you are concerned with using old state for any use case then useState with useEffect needs to be used since it will need to have that state, so approach 1 shall be used in this situation.
If we have to update state only, then a better way can be if we use the push method to do so.
Here is my code. I want to store URLs from Firebase in state.
const [imageUrl, setImageUrl] = useState([]);
const [reload, setReload] = useState(0);
useEffect(() => {
if (reload === 4) {
downloadUrl1();
}
}, [reload]);
const downloadUrl = async () => {
setImages([]);
try {
for (let i = 0; i < images.length; i++) {
let url = await storage().ref(urls[i].path).getDownloadURL();
imageUrl.push(url);
setImageUrl([...imageUrl]);
console.log(url, 'check', urls.length, 'length', imageUrl.length);
}
}
catch (e) {
console.log(e);
}
};
const handleSubmit = async () => {
setReload(4);
await downloadUrl();
console.log(imageUrl);
console.log('post submitted');
};
This code works to put URLs in state as an array. This might also work for you.
With custom hooks from my library, you can wait for the state values to update:
useAsyncWatcher(...values):watcherFn(peekPrevValue: boolean)=>Promise - is a promise wrapper around useEffect that can wait for updates and return a new value and possibly a previous one if the optional peekPrevValue argument is set to true.
(Live Demo)
import React, { useState, useEffect, useCallback } from "react";
import { useAsyncWatcher } from "use-async-effect2";
function TestComponent(props) {
const [counter, setCounter] = useState(0);
const [text, setText] = useState("");
const textWatcher = useAsyncWatcher(text);
useEffect(() => {
setText(`Counter: ${counter}`);
}, [counter]);
const inc = useCallback(() => {
(async () => {
await new Promise((resolve) => setTimeout(resolve, 1000));
setCounter((counter) => counter + 1);
const updatedText = await textWatcher();
console.log(updatedText);
})();
}, []);
return (
<div className="component">
<div className="caption">useAsyncEffect demo</div>
<div>{counter}</div>
<button onClick={inc}>Inc counter</button>
</div>
);
}
export default TestComponent;
useAsyncDeepState is a deep state implementation (similar to this.setState (patchObject)) whose setter can return a promise synchronized with the internal effect. If the setter is called with no arguments, it does not change the state values, but simply subscribes to state updates. In this case, you can get the state value from anywhere inside your component, since function closures are no longer a hindrance.
(Live Demo)
import React, { useCallback, useEffect } from "react";
import { useAsyncDeepState } from "use-async-effect2";
function TestComponent(props) {
const [state, setState] = useAsyncDeepState({
counter: 0,
computedCounter: 0
});
useEffect(() => {
setState(({ counter }) => ({
computedCounter: counter * 2
}));
}, [state.counter]);
const inc = useCallback(() => {
(async () => {
await new Promise((resolve) => setTimeout(resolve, 1000));
await setState(({ counter }) => ({ counter: counter + 1 }));
console.log("computedCounter=", state.computedCounter);
})();
});
return (
<div className="component">
<div className="caption">useAsyncDeepState demo</div>
<div>state.counter : {state.counter}</div>
<div>state.computedCounter : {state.computedCounter}</div>
<button onClick={() => inc()}>Inc counter</button>
</div>
);
}
var [state,setState]=useState(defaultValue)
useEffect(()=>{
var updatedState
setState(currentState=>{ // Do not change the state by get the updated state
updateState=currentState
return currentState
})
alert(updateState) // the current state.
})
Without any addtional NPM package
//...
const BackendPageListing = () => {
const [ myData, setMyData] = useState( {
id: 1,
content: "abc"
})
const myFunction = ( x ) => {
setPagenateInfo({
...myData,
content: x
})
console.log(myData) // not reflecting change immediately
let myDataNew = {...myData, content: x };
console.log(myDataNew) // Reflecting change immediately
}
return (
<>
<button onClick={()=>{ myFunction("New Content")} }>Update MyData</button>
</>
)
Not saying to do this, but it isn't hard to do what the OP asked without useEffect.
Use a promise to resolve the new state in the body of the setter function:
const getState = <T>(
setState: React.Dispatch<React.SetStateAction<T>>
): Promise<T> => {
return new Promise((resolve) => {
setState((currentState: T) => {
resolve(currentState);
return currentState;
});
});
};
And this is how you use it (example shows the comparison between count and outOfSyncCount/syncCount in the UI rendering):
const App: React.FC = () => {
const [count, setCount] = useState(0);
const [outOfSyncCount, setOutOfSyncCount] = useState(0);
const [syncCount, setSyncCount] = useState(0);
const handleOnClick = async () => {
setCount(count + 1);
// Doesn't work
setOutOfSyncCount(count);
// Works
const newCount = await getState(setCount);
setSyncCount(newCount);
};
return (
<>
<h2>Count = {count}</h2>
<h2>Synced count = {syncCount}</h2>
<h2>Out of sync count = {outOfSyncCount}</h2>
<button onClick={handleOnClick}>Increment</button>
</>
);
};
Use the Background Timer library. It solved my problem.
const timeoutId = BackgroundTimer.setTimeout(() => {
// This will be executed once after 1 seconds
// even when the application is the background
console.log('tac');
}, 1000);
// replace
return <p>hello</p>;
// with
return <p>{JSON.stringify(movies)}</p>;
Now you should see, that your code actually does work. What does not work is the console.log(movies). This is because movies points to the old state. If you move your console.log(movies) outside of useEffect, right above the return, you will see the updated movies object.
PROBLEM:
I have a MERN application that is has a model with a couple of other models in it. The problem that I figured out later is that it saves the _id of the object and not the actual object in the model when you do this
const checkoutHistory = new Schema({
book: { type: mongoose.Schema.Types.ObjectId, ref: 'books',required: true },
checkoutCopiesNum: {type: Number, required: true},
profChosen: { type: mongoose.Schema.Types.ObjectId, ref: 'prof', required: true },
dueDate: {type: String, required: true}
})
The book: part of the object when retreived will be an id some string like "DKKLDFJhdkghhe839kdd" whatever. This is fine because then I guess I can make an API call in the react app later to search for this book. Is this the correct way to do it though?
The other way that I thought of was in the actual endpoint that retrieves the data was to call the findByID functions and set that data. It didn't work though here is the code for that:
const checkoutHistoryMiddle = async (req, res, next) => {
try {
//get the body of the request
const body = req.body
//check for data
if(!body){
return res.status(400).json({
success: false,
error: 'no body given'
})
}
const history = new CheckoutHist(body)
console.log(history)
// await Book.findById({_id: history.book}, (err, book) => {
// history.book = book
// })
// await Prof.findById({_id: history.profChosen}, (err, prof) => history.profChosen = prof)
console.log(history)
history.save().then(() => next()).catch(error => {
return res.status(400).json({
success: false,
message: error,
msg: "checkout save failed"
})
})
} catch (error) {
res.status(400).json({
success: false,
message: error,
msg: "checkoutHist failed"
})
}
}
I commented out the part I was talking about because well, it didn't work. It still saved the id instead of the object. Which like I said is fine. I gave my other idea a go and decided to do the calls inside the react app.
So I first got the array of objects from the schema provided above like this:
const [bookHist, setBookHist] = useState()
useEffect( () => {
const getHistory = async () => {
api.getCheckoutHist().then(hist => {
setBookHist(hist.data.data.filter((data) => data.book === props.book_id))
})
}
getHistory()
}, [])
This will create an array of objects in bookHist that looks like this
[{_id: "DKJFDKJDKLFJSL", book: "LDKhgajgahgelkji8440skg", checkoutCopiesNum: 3, profChosen: "gjellkdh39gh39kal930alkdfj", dueDate: "11/11/11"}, {...}]
so the next step would be to take each item in the array and get the id to search the database with so api.findProfByID(bookHist[0].profChosen)
then I would need to update the state of bookHist somehow only that item without effect the other items in the array.
The questions I have are what is the best way to update one item in the array state?
How do I make so many api calls? how do I make sure that they are waited on so that the state actually changes once the calls complete?
Here are things I have tried so far:
useEffect(() => {
bookHist.map(async bHist => {
await Axios.get("http://localhost:8174/user/professor/" + bHist.profChosen).then(async prof => {
// console.log(prof)
// console.log(prof)
bHist.profChosen = prof.data.data
// setBookHist(prevStat => ({}))
// setBookHist(...bookHist, [bookHist.])
})
setBookHist(bHist)
})
}, [])
this didn't work I assume because it would not update the state because it is not waiting on the map to finish before it sets the state of bookHist
So then I searched on the internet and found a promisAll method in react like this:
useEffect(() => {
const change = async () => {
if(bookHist){
console.log("prof")
//get the prof data
// const galleries = []
await Promise.all(bookHist.map( (bHist, index) => {
return await Axios.get("http://localhost:8174/user/professor/" + bHist.profChosen);
})).then(someData => {
console.log(someData)
});
}
change()
}, [])
This also does not work for unknown reasons. It only works if it hot reloads and does not refresh. The logging actually logs something when it hot refreshes.
here is the entirety of the funcitional component:
import React, {useState, useEffect} from 'react'
import api from '../../api/index'
import Axios from 'axios'
export default function CheckoutBookHistroy(props){
const [bookHist, setBookHist] = useState()
const [histData, setHistData] = useState([{
book: {},
prof: {}
}])
useEffect( () => {
const getHistory = async () => {
api.getCheckoutHist().then(hist => {
setBookHist(hist.data.data.filter((data) => data.book === props.book_id))
})
}
getHistory()
}, [])
//i also tried this way but this resulted in an infinite loop
const [profChosen, setProfChosen] = useState()
const handleProfFind = async (id) => {
await Axios.get("http://localhost:8174/user/professor/" + id).then(prof => {
setProfChosen(prof.data.data)
})
}
return (
<div>
{
bookHist ?
bookHist.map(data => {
//need to present the prof data here for each data obj
return (
<div>Checked out {data.checkoutCopiesNum}</div>
)}) : <div>no data</div>
}
</div>
)
}
I really hope I can gain some insight into the correct way to do all of this. I must be either really close or awfully wrong. Thank you in advance!
just by looking at your code, i don't see too much issue, although your code is a bit convoluted.
some functions has no caller, ex. handleProfFind. One suggestion, if you want to do something, just do it, no need that many functions, ex.
// assume you only want to do it once after mounting
useEffect( () => {
if (!data) {
api.getCheckoutHist().then(hist => {
// you can set your data state here
// or you can get the id inside each item, and then call more APIs
// whatever you want to do, please finish it here
}
}
}, [])
As the title says, when my state changes in my component, the sub components aren't rerendering.
class App extends Component {
constructor() {
super()
this.state = {
url: ""
}
this.handleWorkerSelect = this.handleWorkerSelect.bind(this)
}
handleWorkerSelect(url) {
this.setState({ url })
}
render() {
return (
<div className="App">
<Workers className="workers" handleClick={this.handleWorkerSelect}/>
<HermesWorker url={this.state.url}/>
</div>
)
}
}
const Workers = (props) => {
return (
<div>
<button onClick={() => props.handleClick("http://localhost:5000/api")}>Worker 1</button>
<button onClick={() => props.handleClick("http://localhost:2000/api")}>Worker 2</button>
</div>
)
}
export default App
here is hermesworker.js
class HermesWorker extends Component {
constructor() {
super()
this.state = {
items: [],
visited: [{name: "This Drive", path: "#back", root: ""}]
}
this.handleFolderClick = this.handleFolderClick.bind(this)
this.handleFileClick = this.handleFileClick.bind(this)
}
componentDidMount() {
if (this.props.url.length === 0) return
fetch(this.props.url)
.then(res => res.json())
.then(items => this.setState({ items }))
}
render() {
const folders = this.state.items.map((item) => {
if (!item.isfile) {
return <Card handleClick={this.handleFolderClick} root={item.root} path={item.path} isfile={item.isfile} name={item.name} size={item.size}/>
}
})
const files = this.state.items.map((item) => {
if (item.isfile) {
return <Card handleClick={this.handleFileClick} root={item.root} path={item.path} isfile={item.isfile} name={item.name} s ize={item.size}/>
}
})
const pathButtons = this.state.visited.map((item) => {
return <PathButton handleClick={this.handleFolderClick} root={item.root} path={item.path} name={item.name}/>
})
return (
<div>
{pathButtons}
<div className="flex-container">
{folders}
{files}
</div>
</div>
)
}
}
Essentially the issue is that the HermesWorker component is not being rerendered to use the new url prop. I am not sure why this is happening because for example, in the hermesworker it renders other subcomponents that do get rerendered during a state change.
Any information is appreciated
EDIT updated to add hermes worker, the file is over 100 lines so i cut out and only pasted the stuff I thought was important to the issue, can supply more if needed
I tested that code and it seems to be working fine. Could you provide What is set in HermesWorker component?
Edit: You'll require to set your state with setState on component updates. To do this, you may look for componentDidUpdate, which will run on every update. This is different from componentDidMount, which (hopefully) will run once and then the component may update and re-render, but re-render it's not considered as "mount". So you may try this instead:
constructor(props) {
super(props);
this.state = {
url: '',
items: [],
visited: [{name: "This Drive", path: "#back", root: ""}]
}
this.fetchData = this.fetchData.bind(this);
}
componentDidMount() {
//Mount Once
}
componentDidUpdate(prevProps, prevState) {
if (this.state.url !== this.props.url) {
this.setState({url: this.props.url});
// Url state has changed.
}
if(prevState.url !== this.state.url){
//run your fetch
this.fetchData();
}
}
fetchData(){
if (this.props.url.length === 0) return
fetch(this.props.url)
.then(res => res.json())
.then(items => this.setState({ items }));
}
Note: I moved the fetch to its own function, but that's completly up to you.
Also notice i added url to the state. Make sure to keep your props set to avoid unexpected behaviours.
Edit 2: componentDidUpdate will hand you prevProps and prevState as parameters. With prevProps you get access to whatever props you got on the previous update, and with prevState, as you may guess, you get access to whatever-your-state-was on the previous update. And by "on the previous update" i mean before the update got executed.
Edit
I've done some more debugging and here is the problem:
CreateProfile.js calls profileActions.createProfile() and passes data to be operated on and this.props.history so that it can push a new path onto the history stack.
profileActions.createProfile() successfully sends data to database. Database successfully uses the data.
profileActions.createProfile() pushes new path onto stack. The component at the path loads and successfully calls a reducer.
The URL in the browser does not reflect the path that is pushed onto the history stack. The new component does not load.
This only happens when creating an entry in the database. When updating an entry, the program works as expected.
I'm currently trying to redirect to a new page with react/redux. On the first submission, the form submits to the backend and creates an entry in the database but fails to redirect to the next page. On the second submission, however, it redirects just fine.
I'm using this.props.history.push() to do the redirect.
I think It may be an issue with the the response received from the backend but I cannot seem to figure out what the issue is. The reason I believe this is because it is hitting different logic because on the second submission, it is updating and not creating an entry.
Here is my component (CreateProfile.js)
import React, { Component } from 'react'
import PropTypes from 'prop-types';
import { withRouter } from 'react-router-dom';
import { connect } from 'react-redux';
import { createProfile } from '../../actions/profileActions';
import TextAreaGroup from '../common/TextAreaGroup';
import InputGroup from '../common/InputGroup';
class CreateProfile extends Component {
// Constructor
// componentWillRecieveProps()
onSubmit = (evt) => {
evt.preventDefault();
const profileData = {
handle: this.state.handle,
bio: this.state.bio,
website: this.state.website,
twitter: this.state.twitter,
instagram: this.state.instagram,
youtube: this.state.youtube,
linkedin: this.state.linkedin,
github: this.state.github,
vsco: this.state.vsco
};
this.props.createProfile(profileData, this.props.history);
}
//onChange()
render() {
// render logic
return (
// markup
<form onSubmit={this.onSubmit}>
// markup
<input
type="submit"
value="Create Profile"
className="btn btn-info btn-block mt-4"
/>
</form>
</div>
</div>
</div>
</div>
)
}
}
CreateProfile.propTypes = {
createProfile: PropTypes.func.isRequired,
profile: PropTypes.object.isRequired,
errors: PropTypes.object.isRequired
};
const mapStateToProps = state => ({
profile: state.profile,
errors: state.errors
});
export default connect(mapStateToProps, { createProfile })(withRouter(CreateProfile));
Here is my action file that submits to the backend (profileActions.js):
import axios from 'axios';
// import types
import { GET_PROFILE, PROFILE_LOADING, GET_ERRORS, CLEAR_CURRENT_PROFILE } from './types';
// Create Profile
export const createProfile = (profileData, history) => dispatch => {
axios.post('/api/profile', profileData)
.then(res => history.push('/login'))
.catch(err => {
dispatch({
type: GET_ERRORS,
payload: err.response.data
})
})
};
}
And here is the route in my backend that is being submitted to:
router.post('/', passport.authenticate('jwt', { session: false }), (req, res) => {
const { errors, isValid } = validateProfileInputs(req.body);
if (!isValid) {
return res.status(400).json(errors);
}
const profileFields = {}; //code setting fields omitted
Profile.findOne({user: req.user.id}).then(profile => {
if (profile) {
// Update Profile
Profile.findOneAndUpdate(
{ user: req.user.id },
{ $set: profileFields },
{ new: true }
).then(profile => res.json(profile)); // SUCCESSFUL PUSH ONTO THIS.PROPS.HISTORY
} else {
// Create Profile
// Check if handle exists
Profile.findOne({ handle: profileFields.handle })
.then(profile => {
if (profile) {
errors.handle = 'That handle already exists';
res.status(400).json(errors);
}
new Profile(profileFields).save().then(profile => res.json(profile)); // PUSH ONTO THIS.PROPS.HISTORY NOT OCCURRING
});
}
});
});
Any and all help would be greatly appreciated. I have tried my hardest but cannot seem to figure out what the issue is.
This problem arose because of my lack of understanding of how asynchronous javascript works.
The issue was with a few lines of code in the component that I was trying to push too.
componentDidMount() {
this.props.getProfile(); // Async function, sets profile object in store
}
render() {
const { profile } = this.state.profile;
if(!Object.keys(profile).length > 0) { // This is always evaluates to true
// because it executes before
// this.props.getProfile() returns
this.props.history.push('/create-profile');
}
}