I wanted to use a function as a react hook to wrap fetch requests to an API.
My current hook:
export function useAPI(url, options={}) {
const [auth, setAuth] = useGlobal('auth');
const [call, setCall] = useState(undefined);
const apiFetch = async () => {
const res = await fetch(url, {
...options,
});
if (!res.ok)
throw await res.json();
return await res.json();
};
function fetchFunction() {
fetch(url, {
...options,
});
}
useEffect(() => {
// Only set function if undefined, to prevent setting unnecessarily
if (call === undefined) {
setCall(fetchFunction);
//setCall(apiFetch);
}
}, [auth]);
return call
}
That way, in a react function, I could do the following...
export default function LayoutDash(props) {
const fetchData = useAPI('/api/groups/mine/'); // should return a function
useEffect(() => {
fetchData(); // call API on mount
}, []);
render(...stuff);
}
But it seems react isn't able to use functions in hooks like that. If I set call to fetchFunction, it returns undefined. If I set it to apiFetch, it executes and returns a promise instead of a function that I can call when I want to in the other component.
I initially went for react hooks because I can't use useGlobal outside react components/hooks. And I would need to have access to the reactn global variable auth to check if the access token is expired.
So what would be the best way to go about this? The end goal is being able to pass (url, options) to a function that will be a wrapper to a fetch request. (It checks if auth.access is expired, and if so, obtains a new access token first, then does the api call, otherwise it just does the API call). If there's another way I should go about this other than react hooks, I'd like to know.
Instead of putting your function into useState, consider using useCallback. Your code would look something like this:
export function useAPI(url, options={}) {
const [auth, setAuth] = useGlobal('auth');
function fetchFunction() {
fetch(url, {
...options,
});
}
const call = useCallback(fetchFunction, [auth]);
const apiFetch = async () => {
const res = await fetch(url, {
...options,
});
if (!res.ok)
throw await res.json();
return await res.json();
};
return call
}
The returned function is recreated whenever auth changes, therefore somewhat mimicking what you tried to do with useEffect
Related
I'm struggling a bit with using custom react hooks.
I got 2 custom hooks.
First hook is for fetching a ID, the second one is used to fetch a profile with this previous fetched ID. It is dependent on that ID so I need to await this promise.
I have the following custom hook:
export const UseMetamask = () => {
//Todo: Create check if metamask is in browser, otherwise throw error
const fetchWallet = async (): Promise<string | null> => {
try {
const accounts: string[] = await window.ethereum.request(
{
method: 'eth_requestAccounts'
},
);
return accounts[0];
} catch(e) {
console.error(e);
return null;
}
}
return fetchWallet();
}
Then in my second hook I have:
const wallet = UseMetamask();
which is then used in a react-query call like:
useQuery(
['user', wallet],
() => getUserByWallet(wallet),
Now it complains on the wallet about it being a Promise<string | null> which is ofcourse not suitable for the getUserByWallet.
What is the go to way to wait for another hook then use that result in a second hook?
Thanks!
A functional component is a synchronous function, and as a component has life cycle hooks. The asynchronous calls are side effects that should be handled by hooks, not by passing promises in the body of the function. See this SO answer.
Option 1 - using useEffect with useState:
Wrap the api call in useEffect and set the wallet state when the api call succeeds. Return the wallet state from the hook:
export const useMetamask = () => {
const [wallet, setWallet] = useState<string | null>(null);
useEffect(() => {
const fetchWallet = async(): Promise<string | null> => {
try {
const accounts: string[] = await window.ethereum.request({
method: 'eth_requestAccounts'
});
setWallet(accounts[0]);
} catch (e) {
console.error(e);
return null;
}
}
fetchWallet();
}, []);
return wallet;
}
Usage:
Get the wallet from the hook. This would be null or the actual value:
const wallet = useMetamask();
Only enable the call when a wallet actually exists (not null). We'll use the enable option (see Dependent Queries), to enable/disable the query according to the value of wallet:
useQuery(
['user', wallet],
() => getUserByWallet(wallet),
{
// The query will not execute until the wallet exists
enabled: !!wallet,
}
)
Option 2 - use two useQuery hooks
Since you already use useQuery, you need to manually write a hook. Just get the wallet from another useQuery call:
const wallet useQuery('wallet', fetchWallet);
useQuery(
['user', wallet],
() => getUserByWallet(wallet),
{
// The query will not execute until the wallet exists
enabled: !!wallet,
}
)
It is a bad idea to create a hook then just return a single function out of it. And it is a promise too on top of that. Return an object from your hook instead. Then await it in your caller.
export const useMetamask = () => {
//Todo: Create check if metamask is in browser, otherwise throw error
const fetchWallet = async (): Promise<string | null> => {
try {
const accounts: string[] = await window.ethereum.request(
{
method: 'eth_requestAccounts'
},
);
return accounts[0];
} catch(e) {
console.error(e);
return null;
}
}
return { fetchWallet };
}
Then in your caller
const { fetchWallet } = useMetamask();
const wallet = await fetchWallet();
useQuery(
['user', wallet],
() => getUserByWallet(wallet),
Also, please use a small letter 'useSomething' in your hooks to differentiate it from your UI components
You need to use useState in the custom hook.
// move fetchWallet function to utils and import it here for better code smells
export const useMetamask = () => {
const [wallet, setWallet] = useState(null);
// you do not want to fetch wallet everytime the component updates, You want to do it only once.
useEffect(()=>{
fetchWallet().then(wallet => setWallet(wallet)).catch(errorHandler);
}, [])
return wallet;
}
In other hooks, check if wallet is null and handle accordingly.
I have an API called getQuote and a component called QuoteCard. Inside QuoteCard I'm trying to render an array of users that liked a quote. The API works fine, I have tested it, and the code below for getting the users works fine too.
const Post = async (url, body) => {
let res = await fetch(url, {
method: "POST",
headers: {
"Content-Type": "application/json",
"accept": "*/*"
},
body: JSON.stringify(body)
}).then(r => r.json());
return res;
}
const getAllLikes = async () => {
let users = await Post('api/getQuote', {
id: "639e3aff914d4c4f65418a1b"
})
return users
}
console.log(getAllLikes())
The result is working as expected :
However, when trying to map this promise result array to render it onto the page is where I have problems. I try to render like this:
<div>
{getAllLikes().map((user) => (
<p>{user}</p>
))}
</div>
However, I get an error that states:
getAllLikes(...).map is not a function
I don't understand why this is happening. Why can't I map the array? Is it because it's a promise or something?
And if anyone needs to see the getQuote API, here it is:
//Look ma I wrote an API by myself! :D
import clientPromise from "../../lib/mongodb";
const ObjectId = require('mongodb').ObjectId;
import nc from "next-connect";
const app = nc()
app.post(async function getQuote(req, res) {
const client = await clientPromise;
const db = client.db("the-quotes-place");
try {
let quote = await db.collection('quotes').findOne({
_id: new ObjectId(req.body.id)
})
res.status(200).json(JSON.parse(JSON.stringify(quote.likes.by)));
} catch (e) {
res.status(500).json({
message: "Error getting quote",
success: false
})
console.error(e);
}
})
export default app
Thanks for any help!
It is due to the fact that getAllLikes is an async function and thus it returns promise which does not have a map function.
You can either save it in a state variable before using await Or chain it with .then.
Minimal reproducible example which works
const getAllLikes = async () => {
return ['a', 'b']
}
getAllLikes().then((r) => r.map((g) => { console.log(g) }))
Edit: The above code won't work if directly used with jsx since the return of getAllLikes will still be a promise. Solution would be to save it in a state variable and then using it.
I am from Angular and I believe we call pipe on Observables (or Promises). Map can then be called inside the pipe function
observable$ = getAllLikes().pipe(map( user => <p>{user}</p>))
If there is no pipe, I can only think of manually subscribing (which is not a good practice)
sub$ = getAllLikes().subscribe( user => <p>{user}</p>)
// unsub from sub$ appropriately
// We do this from ngOnDestroy in angular
ngOnDestroy() {
this.sub$?.unsubscribe()
}
I have two async functions which reach out to API endpoints (Serverless Framework) - one gets and returns a token, the other gets and returns data using the token.
I'm testing these by using simple buttons, where onClick calls the functions to pull the token and the data, respectively. Click one button to get the token, which is saved to state. Then, once I see the token has been received, I click the other button to get the data. This works without any issues at all.
The problem is when I try calling them sequentially from the React app. I need to call these back-to-back when the user submits a request. I can't seem to make the code wait for the token to arrive before trying to pull the data.
The functions being called in the onClick method of the button:
const tokenBtnOnClick = () =>
{
const response = getToken().then(x => {
setToken(x.data.response.token)
})
}
const dataBtnOnClick = () =>
{
const response = getData(token, param1, param2, param3).then(x => {
setData(x.data.response)
})
}
Async functions:
export async function getToken()
{
const apiUrl = `${BASE_URL}/handler/getToken`
const axios = require('axios').default
let response
try
{
response = await axios.get(apiUrl)
}
catch (e)
{
console.log(e)
}
if (response)
{
return response
}
else
{
return ''
}
}
export async function getData(token, param1, param2, param3)
{
const apiUrl = `${BASE_URL}/handler/getData?token=${token}¶m1=${param1}¶m2=${param2}¶m3=${param3}`
const axios = require('axios').default
let response
try
{
response = await axios.post(apiUrl)
}
catch (e)
{
console.log(e)
}
if (response)
{
return response
}
else
{
return ''
}
}
I've tried calling this getBoth() function in a single button's onClick:
async function getBoth()
{
const tokenResponse = await tokenBtnOnClick().then(x => setToken(x.data.response.token))
const dataResponse = await dataBtnOnClick().then(x => setData(x.data.response))
}
But even though it's an async function that uses await on both lines, I always get the same TypeError because dataBtnOnClick is called immediately, without actually waiting for the token to come in. When I run this code, tokenBtnOnClick is called, the app crashes due to a TypeError, and then the token comes in and is logged and saved to state.
I've also tried this: (where getData is exactly as above, but now accepts token as a paramter rather than using the state variable)
async function getBoth()
{
const response = await getToken().then(x => getData(x.data.response.token))
}
index.js?bee7:59 Uncaught (in promise) TypeError: Cannot read
properties of undefined (reading 'then')
How do I get this to actually wait for the token to come in before trying to pull the data?
You are calling setToken and expection token to be updated immediately, but setToken will be asynchronously applied.
Can you useEffect to solve your problem?
useEffect(() => {
getData(token, param1, param2, param3).then(x => {
setData(x.data.response)
})
}, [token])
Try this
const tokenBtnOnClick = () =>{
setToken(getToken())
}
const dataBtnOnClick = () =>{
setData(getData(token, param1, param2, param3))
}
and
const axios = require('axios').default
export async function getToken()
let apiUrl = `${BASE_URL}/handler/getToken`
{
let response = await axios.get(apiUrl)
return response.data.token;
//i don't know exactly what the api returns so it may be diferent
}
export async function getData(token, param1, param2, param3)
{
let apiUrl = `${BASE_URL}/handler/getData? token=${token}¶m1=${param1}¶m2=${param2}¶m3=${param3}`
let response = await axios.post(apiUrl)
return response.data.response;
}
and in your getBoth() just call them because the functions are asynchronous the code will only move forward after them are finished
getBoth(){
setToken(getToken())
setData(getData(token, param1, param2, param3))
}
Does anyone know why this fetch continues to fire. I have also tried putting it inside a useEffect with no luck. It should only fire once to return once imdbID has loaded.
const WatchOnList = ({ imdbId }) => {
const [locations, setLocations] = useState([])
var headers = new Headers();
headers.append("x-api-key", "API_KEY")
var requestOptions = {
method: 'GET',
headers: headers,
crossDomain: true,
redirect: 'follow'
};
async function fetchData() {
const res = await fetch(`${awsApiUrl}?imdb_id=${imdbId}`, requestOptions);
res
.json()
.then((res) => {
setLocations(res)
console.log(locations)
})
.catch(error => console.log('error', error));
}
fetchData();
With the current structure, the request will fire on every re-render. Which will be quite often in a React app. useEffect is the right place for such a function. But there are some caveats:
You can't make useEffect async, you have to create an async function inside the hook instead and call it afterward.
useEffect will per default run on every update, so you have to tell it explicitly to only run once (like componentDidMount for class components). This can be done by passing an empty array as the second parameter. The hook watches parameters specified in this array and only updates when one of them changes. As it is empty, it only fires once on initialization.
This should work:
useEffect(() => {
async function fetchData() {
const res = await fetch(`${awsApiUrl}?imdb_id=${imdbId}`, requestOptions);
res
.json()
.then(res => {
setLocations(res);
console.log(locations);
})
.catch(error => console.log("error", error));
}
fetchData();
}, []);
Read more about the behavior of hooks here and here.
I have a React application and I have a centralized API Class. So All of the API calls I make, go through APIClass. I call a specific function of an API class with props and that fetches the data using APICaller and returns it asynchronously. The problem is that I need to implement axios cancel token for it and not sure how could I achieve it. In the below setup, callAPIone would return the data while callAPItwo would fail. How can I make it so second call would cancel first one?
let i = await this.apiClass.callAPIone(1);
let y = await this.apiClass.callAPIone(2,cancel);
Then within apiClass, I have functions like
callAPIone = async (param,cancel) => {
return await ApiCaller(param,cancel)
}
Then within ApiCaller I have
async function ApiCaller(param,apiCancel) {
let source = axios.CancelToken.source();
if (apiCancel) source.cancel("Request canceled.");
let params = param
return await axios
.get(apiRoute, { headers, params, cancelToken: source.token })
.then((response) => OnSuccess(response))
.catch((e) => OnError(e.message));
}