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I have a context provider in my app:
export const FormContext = createContext<IFormContext | null>(null);
function FormProvider({ caseNumber, children, ...props }: PropsWithChildren<IFormProviderContextProps>) {
const {
data: { caseNumber, taxDocuments, roles },
api,
} = useApiData();
const [error, setError] = useState<string>(null);
const [searchParams, setSearchParams] = useSearchParams();
const activeStep = searchParams.get("step");
const setActiveStep = useCallback((x: number) => {
searchParams.delete("steg");
setSearchParams([...searchParams.entries(), ["step", Object.keys(STEPS).find((k) => STEPS[k] === x)]]);
}, []);
useEffect(() => {
const abortController = new AbortController();
if (case) api.getPersons(case, abortController.signal).catch((error) => setError(error.message));
return () => {
abortController.abort();
};
}, [case]);
useEffect(() => {
const abortController = new AbortController();
if (activeStep === Stepper.INCOME) {
api.getTaxDocuments(abortController.signal).catch((error) => setError(error.message));
}
return () => {
abortController.abort();
};
}, [activeStep]);
useEffect(() => {
const abortController = new AbortController();
api.getCase(caseNumber, abortController.signal).catch((error) => setError(error.message));
}
return () => {
abortController.abort();
};
}, []);
return (
<FormContex.Provider value={{ taxDocuments, case, roles, activeStep, setActiveStep, error, ...props }}>
{children}
</FormContex.Provider>
);
}
I am using this FormProvider as a wrapper for my FormPage:
<React.StrictMode>
<BrowserRouter>
<Routes>
<Route path="/:caseNumber" element={<FormWrapper />} />
<Route path="/" element={<div>Hello world</div>} />
</Routes>
</BrowserRouter>
</React.StrictMode>
function FormWrapper() {
const { caseNumber } = useParams<{ caseNumber?: string }>();
return (
<FormProvider caseNumber={caseNumber}>
<FormPage />
</FormProvider>
);
}
In my FormPage I display components based on the activeStep that I get from FromProvider
export default function FormWrapper({ activeStep, ...props }: FormWrapperProps) {
const renderForm = useMemo(() => {
switch (activeStep) {
case Stepper.TIMELINE:
return <Timeline {...props} />;
case Stepper.INCOME:
return <Income {...props} />;
case Stepper.RESIDENCY:
return <Residency {...props} />;
case Stepper.SUMMARY:
return <Summary {...props} />;
default:
return <Timeline {...props} />;
}
}, [activeStep]);
return <Suspense fallback={<Loader size="3xlarge" title="loading..." />}>{renderForm}</Suspense>;
}
What I would like to do is to implement an abort controller if component gets unmounted to stop the fetch request and state update. I have tried that with implementing it inside useEffect functions of the FormProvider. But, that is repetitive and would like to make some kind of function or a hook that would set the abort controller to every request. I am not sure how to do that with the current setup, where I have my api calls defined in useApiData() hook which looks like this:
export const useApiData = () => {
const [case, setCase] = useState<CaseDto>(null);
const [taxDocuments, setTaxDocuments] = useState<TaxDocumentsResponse[]>([]);
const [roles, setRoles] = useState<IRoleUi[]>([]);
const getCase = async (caseNumber: string, signal?: AbortSignal) => {
const case = await CASE_API.case.findMetadataForCase(caseNumber, { signal });
setCase(case.data);
};
const getPersons = async (case: CaseDto, signal?: AbortSignal) => {
const personPromises = case.roles.map((role) =>
PERSON_API.information.getPersonPost(
{ id: role.id },
{ signal }
)
);
const [...persons] = await Promise.all([...personPromises]);
const roles = persons.map((person) => {
const role = case.roles.find((role) => role.id === person.data.id);
if (!role) throw new Error(PERSON_NOT_FOUND);
return { ...role, ...person.data };
});
setRoles(roles);
};
const getTaxDocuments = async (signal?: AbortSignal) => {
const taxDocumentsDtoPromises = [getFullYear() - 1, getFullYear() - 2, getFullYear() - 3].map((year) =>
TAX_API.integration.getTaxDocument(
{
year: year.toString(),
filter: "",
personId: "123",
},
{ signal }
)
);
const [taxDocument1, taxDocument2, taxDocument3] = await Promise.all([...taxDocumentsDtoPromises]);
setTaxDocuments([taxDocument1.data, taxDocument2.data, taxDocument3.data]);
};
const api = {
getCase,
getPersons,
getTaxDocuments,
};
const data = {
case,
roles,
taxDocuments,
};
return { data, api };
}
As I said I would like to be able to call api without having to define abort controller in every useEffect hook, but I am not sure how to achieve some like this for example:
apiWithAbortController.getCase(caseNumber).catch((error) => setError(error.message))}
I have tried with using a custom hook like this:
export const useAbortController = () => {
const abortControllerRef = useRef<AbortController>();
useEffect(() => {
return () => abortControllerRef.current?.abort();
}, []);
const getSignal = useCallback(() => {
if (!abortControllerRef.current) {
abortControllerRef.current = new AbortController();
}
return abortControllerRef.current.signal;
}, []);
return getSignal;
};
That I was using like this in my useApiData:
const signalAbort = useAbortController();
const getCase = async (caseNumber: string) => {
const case = await CASE_API.case.findMetadataForCase(caseNumber, { signal: signalAbort() });
setCase(case.data);
};
But, that didn't work, with that setup none of the fetch calls were made.
Related
Description
I'm creating a state management tool for a small project, using mainly useSyncExternalStore from React, inspired by this video from Jack Herrington https://www.youtube.com/watch?v=ZKlXqrcBx88&ab_channel=JackHerrington.
But, I'm running into a pattern that doesn't look right, which is having to use 2 providers, one to create the state, and the other to initialise it.
The gist of the problem:
I have a property sessionId coming from an HTTP request. Saving it in my store wasn't an issue.
However, once I have a sessionId then all of my POST requests done with notifyBackend should have this sessionId in the request body. And I was able to achieve this requirement using the pattern above, but I don't like it.
Any idea how to make it better ?
Code
CreateStore.jsx (Not important, just providing the code in case)
export default function createStore(initialState) {
function useStoreData(): {
const store = useRef(initialState);
const subscribers = useRef(new Set());
return {
get: useCallback(() => store.current, []),
set: useCallback((value) => {
store.current = { ...store.current, ...value };
subscribers.current.forEach((callback) => callback());
}, []),
subscribe: useCallback((callback) => {
subscribers.current.add(callback);
return () => subscribers.current.delete(callback);
}, []),
};
}
const StoreContext = createContext(null);
function StoreProvider({ children }) {
return (
<StoreContext.Provider value={useStoreData()}>
{children}
</StoreContext.Provider>
);
}
function useStore(selector) {
const store = useContext(StoreContext);
const state = useSyncExternalStore(
store.subscribe,
() => selector(store.get()),
() => selector(initialState),
);
// [value, appendToStore]
return [state, store.set];
}
return {
StoreProvider,
useStore,
};
}
Creating the state
export const { StoreProvider, useStore } = createStore({
sessionId: "INITIAL",
notifyBackend: () => { },
});
index.jsx
<Router>
<StoreProvider>
<InitialisationProvider>
<App />
</InitialisationProvider>
</StoreProvider>
</Router
InitialisationContext.jsx
const InitialisationContext = createContext({});
export const InitializationProvider = ({ children }) {
const [sessionId, appendToStore] = useStore(store => store.session);
const notifyBackend = async({ data }) => {
const _data = {
...data,
sessionId,
};
try {
const result = await fetchPOST(data);
if (result.sessionId) {
appendToStore({ sessionId: result.sessionId });
} else if (result.otherProp) {
appendToStore({ otherProp: result.otherProp });
}
} catch (e) { }
};
useEffect(() => {
appendToStore({ notifyBackend });
}, [sessionId]);
return (
<InitialisationContext.Provider value={{}}>
{children}
</InitialisationContext.Provider>
);
}
I just tried out Zustand, and it's very similar to what I'm trying to achieve.
Feels like I'm trying to reinvent the wheel.
With Zustand:
main-store.js
import create from 'zustand';
export const useMainStore = create((set, get) => ({
sessionId: 'INITIAL',
otherProp: '',
notifyBackend: async ({ data }) => {
const _data = {
...data,
sessionId: get().sessionId,
};
try {
const result = await fetchPOST(data);
if (result.sessionId) {
set({ sessionId: result.sessionId });
} else if (result.otherProp) {
set({ otherProp: result.otherProp });
}
} catch (e) { }
},
}));
SomeComponent.jsx
export const SomeComponent() {
const sessionId = useMainStore(state => state.sessionId);
const notifyBackend = useMainStore(state => state.notifyBackend);
useEffect(() => {
if (sessionId === 'INITIAL') {
notifyBackend();
}
}, [sessionId]);
return <h1>Foo</h1>
};
This answer focuses on OPs approach to createStore(). After reading the question a few more times, I think there are bigger issues. I'll try to get to these and then extend the answer.
Your approach is too complicated.
First, the store is no hook! It lives completely outside of react. useSyncExternalStore and the two methods subscribe and getSnapshot are what integrates the store into react.
And as the store lives outside of react, you don't need a Context at all.
Just do const whatever = useSyncExternalStore(myStore.subscribe, myStore.getSnapshot);
Here my version of minimal createStore() basically a global/shared useState()
export function createStore(initialValue) {
// subscription
const listeners = new Set();
const subscribe = (callback) => {
listeners.add(callback);
return () => listeners.delete(callback);
}
const dispatch = () => {
for (const callback of listeners) callback();
}
// value management
let value = typeof initialValue === "function" ?
initialValue() :
initialValue;
// this is what useStore() will return.
const getSnapshot = () => [value, setState];
// the same logic as in `setState(newValue)` or `setState(prev => newValue)`
const setState = (arg) => {
let prev = value;
value = typeof arg === "function" ? arg(prev) : arg;
if (value !== prev) dispatch(); // only notify listener on actual change.
}
// returning just a custom hook
return () => useSyncExternalStore(subscribe, getSnapshot);
}
And the usage
export const useMyCustomStore = createStore({});
// ...
const [value, setValue] = useMyCustomStore();
Disclaimer: Please don't mark this as duplicate. I've seen similar questions with answers. But none of them is working for me. I'm just learning React.
What I'm trying to achieve is basically infinite scrolling. So that when a user scrolls to the end of the page, more data will load.
I've used scroll eventListener to achieve this. And it is working.
But I'm facing problems with the state of the variables.
First, I've changed the loading state to true. Then fetch data and set the state to false.
Second, when scrolling to the end of the page occurs, I again change the loading state to true. Add 1 with pageNo. Then again fetch data and set the loading state to false.
The problems are:
loading state somehow remains true.
Changing the pageNo state is not working. pageNo always remains to 1.
And actually none of the states are working as expected.
My goal: (Sequential)
Set loading to true.
Fetch 10 posts from API after component initialization.
Set loading to false.
After the user scrolls end of the page, add 1 with pageNo.
Repeat Step 1 to Step 3 until all posts loaded.
After getting an empty response from API set allPostsLoaded to true.
What I've tried:
I've tried adding all the states into dependencyList array of useEffect hook. But then an infinite loop occurs.
I've also tried adding only pageNo and loading state to the array, but same infinite loop occurs.
Source:
import React, { lazy, useState } from 'react';
import { PostSection } from './Home.styles';
import { BlogPost } from '../../models/BlogPost';
import { PostService } from '../../services/PostService';
const defaultPosts: BlogPost[] = [{
Id: 'asdfg',
Content: 'Hi, this is demo content',
Title: 'Demo title',
sections: [],
subTitle: '',
ReadTime: 1,
CreatedDate: new Date()
}];
const defaultPageNo = 1;
const PostCardComponent = lazy(() => import('./../PostCard/PostCard'));
const postService = new PostService();
const Home = (props: any) => {
const [posts, setPosts]: [BlogPost[], (posts: BlogPost[]) => void] = useState(defaultPosts);
const [pageNo, setPageNo] = useState(defaultPageNo);
const [pageSize, setPageSize] = useState(10);
const [loading, setLoading] = useState(false);
const [allPostsLoaded, setAllPostsLoaded] = useState(false);
const [featuredPost, setFeaturedPost]: [BlogPost, (featuredPost: BlogPost) => void] = useState(defaultPosts[0]);
async function getPosts() {
return await postService.getPosts(pageSize, pageNo);
}
async function getFeaturedPost() {
return await postService.getFeaturedPost();
}
function handleScroll(event: any) {
console.log('loading ' + loading);
console.log('allPostsLoaded ' + allPostsLoaded);
var target = event.target.scrollingElement;
if (!loading && !allPostsLoaded && target.scrollTop + target.clientHeight === target.scrollHeight) {
setLoading(true);
setPageNo(pageNo => pageNo + 1);
setTimeout(()=>{
getPosts()
.then(response => {
const newPosts = response.data.data;
setLoading(false);
if (newPosts.length) {
const temp = [ ...posts ];
newPosts.forEach(post => !temp.map(m => m.Id).includes(post.Id) ? temp.push(post) : null);
setPosts(temp);
} else {
setAllPostsLoaded(true);
}
})
}, 1000);
}
}
function init() {
setLoading(true);
Promise.all([getFeaturedPost(), getPosts()])
.then(
responses => {
setLoading(false);
setFeaturedPost(responses[0].data.data);
setPosts(responses[1].data.data);
}
);
}
React.useEffect(() => {
window.addEventListener("scroll", handleScroll);
init();
return () => {
window.removeEventListener("scroll", handleScroll);
};
}, []
);
return (
<PostSection className="px-3 py-5 p-md-5">
<div className="container">
<div className="item mb-5">
{posts.map(post => (
<PostCardComponent
key={post.Id}
Title={post.Title}
intro={post.Content}
Id={post.Id}
ReadTime={post.ReadTime}
CreatedDate={post.CreatedDate}
/>
))}
</div>
</div>
</PostSection>
);
};
export default Home;
Used more effects to handle the change of pageNo, loader and allPostsLoaded state worked for me.
Updated Source:
import React, { lazy, useState } from 'react';
import { Guid } from "guid-typescript";
import { PostSection } from './Home.styles';
import { BlogPost } from '../../models/BlogPost';
import { PostService } from '../../services/PostService';
import { Skeleton } from 'antd';
const defaultPosts: BlogPost[] = [{
Id: '456858568568568',
Content: 'Hi, this is demo content. There could have been much more content.',
Title: 'This is a demo title',
sections: [],
subTitle: '',
ReadTime: 1,
CreatedDate: new Date()
}];
const defaultPageNo = 1;
const defaultPageSize = 10;
const PostCardComponent = lazy(() => import('./../PostCard/PostCard'));
const postService = new PostService();
const Home: React.FC<any> = props => {
const [posts, setPosts]: [BlogPost[], (posts: BlogPost[]) => void] = useState(defaultPosts);
const [pageNo, setPageNo] = useState(defaultPageNo);
const [pageSize, setPageSize] = useState(defaultPageSize);
const [loading, setLoading] = useState(false);
const [allPostsLoaded, setAllPostsLoaded] = useState(false);
const [featuredPost, setFeaturedPost]: [BlogPost, (featuredPost: BlogPost) => void] = useState(defaultPosts[0]);
function getNewGuid() {
return Guid.create().toString();
}
async function getPosts() {
return await postService.getPosts(pageSize, pageNo);
}
async function getFeaturedPost() {
return await postService.getFeaturedPost();
}
function init() {
setLoading(true);
Promise.all([getFeaturedPost(), getPosts()])
.then(
responses => {
setLoading(false);
setFeaturedPost(responses[0].data.data);
setPosts(responses[1].data.data);
}
);
}
React.useEffect(() => {
init();
return;
}, []);
React.useEffect(() => {
if (allPostsLoaded || loading) return;
function handleScroll(event: any) {
var target = event.target.scrollingElement;
if (!loading && !allPostsLoaded && target.scrollTop + target.clientHeight === target.scrollHeight) {
setPageNo(pageNo => pageNo+1);
}
}
window.addEventListener("scroll", handleScroll);
return () => {
window.removeEventListener("scroll", handleScroll);
};
}, [loading, allPostsLoaded]
);
React.useEffect(() => {
if (pageNo > 1) {
setLoading(true);
setTimeout(()=>{
getPosts()
.then(response => {
const newPosts = response.data.data;
setTimeout(()=>{
setLoading(false);
if (newPosts.length) {
const temp = [ ...posts ];
newPosts.forEach(post => !temp.map(m => m.Id).includes(post.Id) ? temp.push(post) : null);
setPosts(temp);
} else {
setAllPostsLoaded(true);
}
}, 1000);
})
}, 1000);
}
}, [pageNo]
);
return (
<PostSection className="px-3 py-5 p-md-5">
<div className="container">
<div className="item mb-5">
{posts.map(post => (
<PostCardComponent
key={post.Id}
Title={post.Title}
intro={post.Content}
Id={post.Id}
ReadTime={post.ReadTime}
CreatedDate={post.CreatedDate}
/>
))}
</div>
</div>
</PostSection>
);
};
export default Home;
So i am using a HOC for general error handling purposes in react like this:
import React, { useState, useEffect } from 'react'
import Modal from '../../UI/Modal/Modal'
const WithErrorHandler = (WrappedComponent, axios) => {
const NewComponent = props => {
console.log('UseState')
const [error, setError] = useState(null)
console.log('runs')
useEffect(() => {
const req = axios.interceptors.request.use(config => {
console.log('request intercepted')
return config
})
const res = axios.interceptors.response.use(null, error => {
setError(error)
return Promise.reject(error)
})
return () => {
axios.interceptors.request.eject(req)
axios.interceptors.response.eject(res)
}
}, [])
return (
<div>
{console.log('render')}
{error ? (
<Modal clickHandler={() => setError(null)}> {error.message}</Modal>
) : null}
<WrappedComponent {...props} />
</div>
)
}
return NewComponent
}
export default WithErrorHandler
The problem i have run into is that i have a component which fires an axios request in it's useEffect().
When i try to wrap this component with my WithErrorHandler the useEffect of the wrapped component fires first then the useEffect of HOC withErrorHandler runs. This causes the axios request to be made faster than the HOC could register the axios interceptors. Any ideas on how to fix this would be aprreciated.
You can define an intermediate state which prevents from rendering wrapped component.
const WithErrorHandler = (WrappedComponent, axios) => {
const NewComponent = (props) => {
const [ready, setReady] = useState(false); // HERE
console.log("UseState");
const [error, setError] = useState(null);
console.log("runs");
useEffect(() => {
const req = axios.interceptors.request.use((config) => {
console.log("request intercepted");
return config;
});
const res = axios.interceptors.response.use(null, (error) => {
setError(error);
return Promise.reject(error);
});
setReady(true); // HERE
return () => {
axios.interceptors.request.eject(req);
axios.interceptors.response.eject(res);
};
}, []);
if (!ready) return null; // HERE
return (
<div>
{console.log("render")}
{error ? (
<Modal clickHandler={() => setError(null)}> {error.message}</Modal>
) : null}
<WrappedComponent {...props} />
</div>
);
};
return NewComponent;
};
What it does is that it makes sure that axios interceptor is initialized and it is good to render wrapped component.
Instead of if (!ready) return null; you can return a more sensible state from your HOC for instance, if (!ready) return <p>Initializing...</p>
You need an extra render for the NewComponent callback to run, adding a conditional rendering on WrappedComponent should do the trick.
Notice that we set isFirstRender on promise success, change it dependenly on your use case.
const WithErrorHandler = (WrappedComponent, axios) => {
const NewComponent = (props) => {
const [isFirstRender, setIsFirstRender] = useState(true);
const [error, setError] = useState(null);
useEffect(() => {
if (isFirstRender) {
const req = axios.interceptors.request.use((config) => {
return config;
});
// Check req success
if (req.isSuccess) { setIsFirstRender(false); }
const res = axios.interceptors.response.use(null, (error) => {
setError(error);
return Promise.reject(error);
});
return () => {
axios.interceptors.request.eject(req);
axios.interceptors.response.eject(res);
};
}
}, [isFirstRender]);
return (
<div>
{error ? (
<Modal clickHandler={() => setError(null)}> {error.message}</Modal>
) : null}
{!isFirstRender && <WrappedComponent {...props} />}
</div>
);
};
return NewComponent;
};
I have fetch method in useEffect hook:
export const CardDetails = () => {
const [ card, getCardDetails ] = useState();
const { id } = useParams();
useEffect(() => {
fetch(`http://localhost:3001/cards/${id}`)
.then((res) => res.json())
.then((data) => getCardDetails(data))
}, [id])
return (
<DetailsRow data={card} />
)
}
But then inside DetailsRow component this data is not defined, which means that I render this component before data is fetched. How to solve it properly?
Just don't render it when the data is undefined:
export const CardDetails = () => {
const [card, setCard] = useState();
const { id } = useParams();
useEffect(() => {
fetch(`http://localhost:3001/cards/${id}`)
.then((res) => res.json())
.then((data) => setCard(data));
}, [id]);
if (card === undefined) {
return <>Still loading...</>;
}
return <DetailsRow data={card} />;
};
There are 3 ways to not render component if there aren't any data yet.
{data && <Component data={data} />}
Check if(!data) { return null } before render. This method will prevent All component render until there aren't any data.
Use some <Loading /> component and ternar operator inside JSX. In this case you will be able to render all another parts of component which are not needed data -> {data ? <Component data={data} /> : <Loading>}
If you want to display some default data for user instead of a loading spinner while waiting for server data. Here is a code of a react hook which can fetch data before redering.
import { useEffect, useState } from "react"
var receivedData: any = null
type Listener = (state: boolean, data: any) => void
export type Fetcher = () => Promise<any>
type TopFetch = [
loadingStatus: boolean,
data: any,
]
type AddListener = (cb: Listener) => number
type RemoveListener = (id: number) => void
interface ReturnFromTopFetch {
addListener: AddListener,
removeListener: RemoveListener
}
type StartTopFetch = (fetcher: Fetcher) => ReturnFromTopFetch
export const startTopFetch = function (fetcher: Fetcher) {
let receivedData: any = null
let listener: Listener[] = []
function addListener(cb: Listener): number {
if (receivedData) {
cb(false, receivedData)
return 0
}
else {
listener.push(cb)
console.log("listenre:", listener)
return listener.length - 1
}
}
function removeListener(id: number) {
console.log("before remove listener: ", id)
if (id && id >= 0 && id < listener.length) {
listener.splice(id, 1)
}
}
let res = fetcher()
if (typeof res.then === "undefined") {
receivedData = res
}
else {
fetcher().then(
(data: any) => {
receivedData = data
},
).finally(() => {
listener.forEach((cb) => cb(false, receivedData))
})
}
return { addListener, removeListener }
} as StartTopFetch
export const useTopFetch = (listener: ReturnFromTopFetch): TopFetch => {
const [loadingStatus, setLoadingStatus] = useState(true)
useEffect(() => {
const id = listener.addListener((v: boolean, data: any) => {
setLoadingStatus(v)
receivedData = data
})
console.log("add listener")
return () => listener.removeListener(id)
}, [listener])
return [loadingStatus, receivedData]
}
This is what myself needed and couldn't find some simple library so I took some time to code one. it works great and here is a demo:
import { startTopFetch, useTopFetch } from "./topFetch";
// a fakeFetch
const fakeFetch = async () => {
const p = new Promise<object>((resolve, reject) => {
setTimeout(() => {
resolve({ value: "Data from the server" })
}, 1000)
})
return p
}
//Usage: call startTopFetch before your component function and pass a callback function, callback function type: ()=>Promise<any>
const myTopFetch = startTopFetch(fakeFetch)
export const Demo = () => {
const defaultData = { value: "Default Data" }
//In your component , call useTopFetch and pass the return value from startTopFetch.
const [isloading, dataFromServer] = useTopFetch(myTopFetch)
return <>
{isloading ? (
<div>{defaultData.value}</div>
) : (
<div>{dataFromServer.value}</div>
)}
</>
}
Try this:
export const CardDetails = () => {
const [card, setCard] = useState();
const { id } = useParams();
useEffect(() => {
if (!data) {
fetch(`http://localhost:3001/cards/${id}`)
.then((res) => res.json())
.then((data) => setCard(data))
}
}, [id, data]);
return (
<div>
{data && <DetailsRow data={card} />}
{!data && <p>loading...</p>}
</div>
);
};
I have this code
import ReactDOM from "react-dom";
import React, { useState, useEffect } from "react";
import { BrowserRouter as Router, Route, Link } from "react-router-dom";
function ParamsExample() {
return (
<Router>
<div>
<h2>Accounts</h2>
<Link to="/">Netflix</Link>
<Route path="/" component={Miliko} />
</div>
</Router>
);
}
const Miliko = ({ match }) => {
const [data, setData] = useState([]);
const [isLoading, setIsLoading] = useState(false);
const [isError, setIsError] = useState(false);
useEffect(() => {
(async function() {
setIsError(false);
setIsLoading(true);
try {
const Res = await fetch("https://foo0022.firebaseio.com/New.json");
const ResObj = await Res.json();
const ResArr = await Object.values(ResObj).flat();
setData(ResArr);
} catch (error) {
setIsError(true);
}
setIsLoading(false);
})();
console.log(data);
}, [match]);
return <div>{`${isLoading}${isError}`}</div>;
};
function App() {
return (
<div className="App">
<ParamsExample />
</div>
);
}
const rootElement = document.getElementById("root");
ReactDOM.render(<App />, rootElement);
I created three links that open the Miliko component. but when I quickly click on the links I get this error:
To fix, cancel all subscriptions and asynchronous tasks in a useEffect
cleanup function.
I think the problem is caused by dismount before async call finished.
const useAsync = () => {
const [data, setData] = useState(null)
const mountedRef = useRef(true)
const execute = useCallback(() => {
setLoading(true)
return asyncFunc()
.then(res => {
if (!mountedRef.current) return null
setData(res)
return res
})
}, [])
useEffect(() => {
return () => {
mountedRef.current = false
}
}, [])
}
mountedRef is used here to indicate if the component is still mounted. And if so, continue the async call to update component state, otherwise, skip them.
This should be the main reason to not end up with a memory leak (access cleanedup memory) issue.
Demo
https://codepen.io/windmaomao/pen/jOLaOxO , fetch with useAsync
https://codepen.io/windmaomao/pen/GRvOgoa , manual fetch with useAsync
Update
The above answer leads to the following component that we use inside our team.
/**
* A hook to fetch async data.
* #class useAsync
* #borrows useAsyncObject
* #param {object} _ props
* #param {async} _.asyncFunc Promise like async function
* #param {bool} _.immediate=false Invoke the function immediately
* #param {object} _.funcParams Function initial parameters
* #param {object} _.initialData Initial data
* #returns {useAsyncObject} Async object
* #example
* const { execute, loading, data, error } = useAync({
* asyncFunc: async () => { return 'data' },
* immediate: false,
* funcParams: { data: '1' },
* initialData: 'Hello'
* })
*/
const useAsync = (props = initialProps) => {
const {
asyncFunc, immediate, funcParams, initialData
} = {
...initialProps,
...props
}
const [loading, setLoading] = useState(immediate)
const [data, setData] = useState(initialData)
const [error, setError] = useState(null)
const mountedRef = useRef(true)
const execute = useCallback(params => {
setLoading(true)
return asyncFunc({ ...funcParams, ...params })
.then(res => {
if (!mountedRef.current) return null
setData(res)
setError(null)
setLoading(false)
return res
})
.catch(err => {
if (!mountedRef.current) return null
setError(err)
setLoading(false)
throw err
})
}, [asyncFunc, funcParams])
useEffect(() => {
if (immediate) {
execute(funcParams)
}
return () => {
mountedRef.current = false
}
// eslint-disable-next-line react-hooks/exhaustive-deps
}, [])
return {
execute,
loading,
data,
error
}
}
Update 2022
This approach has been adopted in the book https://www.amazon.com/Designing-React-Hooks-Right-Way/dp/1803235950 where this topic has been mentioned in useRef and custom hooks chapters, and more examples are provided there.
useEffect will try to keep communications with your data-fetching procedure even while the component has unmounted. Since this is an anti-pattern and exposes your application to memory leakage, cancelling the subscription to useEffect optimizes your app.
In the simple implementation example below, you'd use a flag (isSubscribed) to determine when to cancel your subscription. At the end of the effect, you'd make a call to clean up.
export const useUserData = () => {
const initialState = {
user: {},
error: null
}
const [state, setState] = useState(initialState);
useEffect(() => {
// clean up controller
let isSubscribed = true;
// Try to communicate with sever API
fetch(SERVER_URI)
.then(response => response.json())
.then(data => isSubscribed ? setState(prevState => ({
...prevState, user: data
})) : null)
.catch(error => {
if (isSubscribed) {
setState(prevState => ({
...prevState,
error
}));
}
})
// cancel subscription to useEffect
return () => (isSubscribed = false)
}, []);
return state
}
You can read up more from this blog juliangaramendy
Without #windmaomao answer, I could spend other hours trying to figure out how to cancel the subscription.
In short, I used two hooks respectively useCallback to memoize function and useEffect to fetch data.
const fetchSpecificItem = useCallback(async ({ itemId }) => {
try {
... fetch data
/*
Before you setState ensure the component is mounted
otherwise, return null and don't allow to unmounted component.
*/
if (!mountedRef.current) return null;
/*
if the component is mounted feel free to setState
*/
} catch (error) {
... handle errors
}
}, [mountedRef]) // add variable as dependency
I used useEffect to fetch data.
I could not call the function inside effect simply because hooks can not be called inside a function.
useEffect(() => {
fetchSpecificItem(input);
return () => {
mountedRef.current = false; // clean up function
};
}, [input, fetchSpecificItem]); // add function as dependency
Thanks, everyone your contribution helped me to learn more about the usage of hooks.
fetchData is an async function which will return a promise. But you have invoked it without resolving it. If you need to do any cleanup at component unmount, return a function inside the effect that has your cleanup code. Try this :
const Miliko = () => {
const [data, setData] = useState({ hits: [] });
const [url, setUrl] = useState('http://hn.algolia.com/api/v1/search?query=redux');
const [isLoading, setIsLoading] = useState(false);
const [isError, setIsError] = useState(false);
useEffect(() => {
(async function() {
setIsError(false);
setIsLoading(true);
try {
const result = await axios(url);
setData(result.data);
} catch (error) {
setIsError(true);
}
setIsLoading(false);
})();
return function() {
/**
* Add cleanup code here
*/
};
}, [url]);
return [{ data, isLoading, isError }, setUrl];
};
I would suggest reading the official docs where it is clearly explained along with some more configurable parameters.
Folowing #Niyongabo solution, the way I ended up that fixed it was:
const mountedRef = useRef(true);
const fetchSpecificItem = useCallback(async () => {
try {
const ref = await db
.collection('redeems')
.where('rewardItem.id', '==', reward.id)
.get();
const data = ref.docs.map(doc => ({ id: doc.id, ...doc.data() }));
if (!mountedRef.current) return null;
setRedeems(data);
setIsFetching(false);
} catch (error) {
console.log(error);
}
}, [mountedRef]);
useEffect(() => {
fetchSpecificItem();
return () => {
mountedRef.current = false;
};
}, [fetchSpecificItem]);
Create a mutable ref object and set it to true, and during clean-up toggle its value, to ensure that the component has been unmouted.
const mountedRef = useRef(true)
useEffect(() => {
// CALL YOUR API OR ASYNC FUNCTION HERE
return () => { mountedRef.current = false }
}, [])
const [getAllJobs, setgetAlljobs] = useState();
useEffect(() => {
let mounted = true;
axios.get('apiUrl')
.then(function (response) {
const jobData = response.data;
if (mounted) {
setgetAlljobs(jobData)
}
})
.catch(function (error) {
console.log(error.message)
})
return () => mounted = false;
}, [])
set a variable mounted to true->
then if it is true, mount the function->
in the bottom you return it to unmount it
My case was pretty different from what this questions wants. Still I got the same error.
My case was because I had a 'list', which was rendered by using .map from array. And I needed to use .shift. (to remove first item in array)
If array had just one item, it was ok, but since it had 2 of them -> the first one got 'deleted/shifted' and because I used key={index} (while index was from .map), it assumed, that the second item, which later was first, was the same component as the shifted item..
React kept info from the first item (they were all nodes) and so, if that second node used useEffect(), React threw error, that the component is already dismounted, because the former node with index 0 and key 0 had the same key 0 as the second component.
The second component correctly used useEffect, but React assumed, that it is called by that former node, which was no longer on the scene -> resulting in error.
I fixed this by adding different key prop value (not index), but some unique string.
you can wrap any action as a callback inside checkUnmount
const useUnmounted = () => {
const mountedRef = useRef(true);
useEffect(
() => () => {
mountedRef.current = false;
},
[],
);
const checkUnmount = useCallback(
(cb = () => {}) => {
try {
if (!mountedRef.current) throw new Error('Component is unmounted');
cb();
} catch (error) {
console.log({ error });
}
},
[mountedRef.current],
);
return [checkUnmount, mountedRef.current];
};
import React, { useCallback, useEffect, useRef, useState } from "react";
import { userLoginSuccessAction } from "../../../redux/user-redux/actionCreator";
import { IUser } from "../../../models/user";
import { Navigate } from "react-router";
import XTextField from "../../../x-lib/x-components/x-form-controls/XTextField";
import { useDispatch } from "react-redux";
interface Props {
onViewChange?: (n: number) => void;
userInit?: (user: IUser) => void;
}
interface State {
email: string;
password: string;
hasError?: boolean;
errorMessage?: string;
}
const initialValue = {
email: "eve.holt#reqres.in",
password: "cityslicka",
errorMessage: "",
};
const LoginView: React.FC<Props> = (props) => {
const { onViewChange } = props;
const [state, setState] = useState(initialValue);
const mountedRef = useRef(true);
const dispatch = useDispatch();
const handleEmailChange = useCallback(
(val: string) => {
setState((state) => ({
...state,
email: val,
}));
},
[state.email]
);
const handlePasswordChange = useCallback(
(val: string) => {
setState((state) => ({
...state,
password: val,
}));
},
[state.password]
);
const onUserClick = useCallback( async () => {
// HTTP Call
const data = {email: state.email , password: state.password}
try{
await dispatch(userLoginSuccessAction(data));
<Navigate to = '/' />
setState( (state)=>({
...state,
email: "",
password: ""
}))
}
catch(err){
setState( (state)=>({
...state,
errorMessage: err as string
}))
}
},[mountedRef] )
useEffect(()=>{
onUserClick();
return ()=> {
mountedRef.current = false;
};
},[onUserClick]);
const Error = (): JSX.Element => {
return (
<div
className="alert alert-danger"
role="alert"
style={{ width: "516px", margin: "20px auto 0 auto" }}
>
{state.errorMessage}
</div>
);
};
return (
<div>
<div>
email: "eve.holt#reqres.in"
<span style={{ paddingRight: "20px" }}></span> password: "cityslicka"{" "}
</div>
{state.errorMessage && <Error />}
<form className="form-inline">
<div className="form-group">
<XTextField
label="email"
placeholder="E-Posta"
value={state.email}
onChange={handleEmailChange}
/>
</div>
<div className="form-group my-sm-3">
<XTextField
type="password"
label="password"
placeholder="Şifre"
value={state.password}
onChange={handlePasswordChange}
/>
</div>
<button type="button" className="btn btn-primary" onClick = {onUserClick} >
Giriş Et
</button>
<a
href="#"
onClick={(e) => {
e.preventDefault();
onViewChange && onViewChange(3);
}}
>
Şifremi Unuttum!
</a>
</form>
<p>
Hələdə üye deyilsiniz? <br />
pulsuz registir olmak üçün
<b>
<u>
<a
style={{ fontSize: "18px" }}
href="#"
onClick={(e) => {
e.preventDefault();
onViewChange && onViewChange(2);
}}
>
kilik edin.
</a>
</u>
</b>
</p>
</div>
);
};
export default LoginView;
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
For this problem I used a tricky way
first I deploy a state like this
const [routing,setRouting] = useState(false)
then when my works finished I changed it to true
and change my useEffect like this
useEffect(()=>{
if(routing)
navigation.navigate('AnotherPage')
),[routing]}