Let's say I have an application store with following pages
/stores/:store_id/
/stores/:store_id/products/
/stores/:store_id/products/:produc_id
User can directly access /stores/:store_id/products/:produc_id
Hoever, before loading stores and products.
I need to do a bunch of requests.
/validateUser
/loadUserInfo
However, if the user has already verified, I don't want to call, /validateUser, /loadUserInfo again and again.
Because I have about 50 pages in my application.
I don't want to put above checks 50 times in each page or included in the above pages.
Anyway to run the check first before loading any page?
Of course there is, are you using any routing lib? Even if you aren't you could create high order functions (HOC) to achive your goal.
import React, { useEffect, useState } from "react";
const withAuthentication = (Component) => (props) => {
const [auth, setAuth] = useState(false);
const [isLoading, setLoading] = useState(true);
useEffect(() => {
const checkAuthentication = () => {
setTimeout(() => {
setAuth(true);
setLoading(false);
}, 2000);
};
checkAuthentication();
}, []);
if (isLoading) {
return <div>Loading...</div>;
}
return (
<div>
{auth ? <Component {...props} /> : <div>No permission component</div>}
</div>
);
};
const Div = (props) => {
console.log(props);
return <div>Test</div>;
};
export default function App() {
const Comp = withAuthentication(Div);
return (
<div>
<Comp match={{ params: ["foo"] }} />
</div>
);
}
It's just a fast draft, it could be with a lot of bugs. After this you could wrap all your components into this HOC and they will be kind of safe
Related
I am attempting to render either an Application or Login page depending on whether getUser() returns a user object.
However, in both development and production, a blank page is rendered.
This is the code
export default function index() {
supabase.auth.getUser().then((response) => {
const userData = response.data.user;
console.log(userData);
return userData != undefined || userData != null ? (
<>
<Shell />
<AppView />
</>
) : (
<NoSessionWarn />
);
});
}
I use NextJS's router.push('/application') to route the user to this page, in case that might have something to do with it.
Any idea why this could be showing a blank page? I've tried taking the return block out of the .then() block and still nothing.
Few things:
In React functional components, side effects must be handled inside
a useEffect hook
React components names should be capitalized (Index instead of index in your case).
Most of the time it's a better idea to use strict equality operator since it also checks for the type of the operands.
As a suggestion, you could abstract the logic of the auth checking process into a custom hook. This not only increases the readability of the component, but also makes this logic reusable and you now would have separation of concerns. Your component doesn't know and doesn't care about how the user data is being retrieved, it just uses it.
Putting it all together:
useAuth custom hook:
export const useAuth = () => {
const [user, setUser] = useState(null)
const [isAuthorizing, setIsAuthorizing] = useState(true)
useEffect(() => {
supabase.auth
.getUser()
.then((response) => {
setUser(response.data.user)
})
.catch((err) => {
console.error(err)
})
.finally(() => {
setIsAuthorizing(false)
})
}, [])
return { user, isAuthorizing }
}
Component:
export default function Index() {
const { user, isAuthorizing } = useAuth()
if (isAuthorizing) return <p>Loading</p>
// Being very explicit here about the possible falsy values.
if (user === null || user === undefined) return <NoSessionWarn />
return (
<>
<Shell />
<AppView />
</>
)
}
You need to use the useState hook to re-render when you receive the data.
You need to use the useEffect hook with an empty dependency array to execute getUser() once on mount.
You'll also probably want a loading mechanism while the request is made.
export default function index() {
const [userData, setUserData] = useState(null);
const [loading, setLoading] = useState(true);
useEffect(() => {
supabase.auth.getUser().then((response) => {
setUserData(response.data.user);
setLoading(false);
});
}, []);
if (loading) return <p>Loading...</p>
if (!userData) return <NoSessionWarn />;
return (
<>
<Shell />
<AppView />
</>
);
}
Example: https://stackblitz.com/edit/react-ts-neq5rh?file=App.tsx
Iam newbie and now learning to make customize react hooks
here i am trying to call the function i made in app.js file, i want to use it onClick button. but fail to do so. please help me to find the error and understand it.
import React, {
useEffect,
useState
} from "react";
const useRandomJoke = () => {
const [jokes, setJokes] = useState();
useEffect(() => {
const jokeFetch = async() => {
await fetch("https://api.icndb.com/jokes/random")
//we'll run 2 "then"
.then(
// this will give us response and will return inform of res.json
(res) => res.json()
) //.json is a format
.then((data) => {
setJokes(data.value.joke);
}); // now calling data from te returned values in res.json
};
jokeFetch();
}, []);
return jokes;
};
export default useRandomJoke;
//With onClick function
function App() { const [jokes, setJokes] = useState();
return (
<div className="App">
<h1>Random Jokes</h1>
<p>{jokes}</p>
<button onClick={()=>{setJokes(useRandomJoke)}}>
Click for Jokes</button>
</div>
); } export default App;
`
useRandomJoke is a custom hook. Hooks should only be called at the top level of a component and as the custom hook already has the joke state, you don't need an additional state in the App component.
If you want to get a new joke after the component renders and every time the button gets clicked, you can do this:
const useRandomJoke = () => {
const [joke, setJoke] = useState("");
const fetchJoke = useCallback(() => {
fetch("https://api.icndb.com/jokes/random")
.then((res) => res.json())
.then((data) => {
setJoke(data.value.joke);
});
}, []);
return [joke, fetchJoke];
};
export default function App() {
const [joke, fetchJoke] = useRandomJoke();
useEffect(() => {
fetchJoke();
}, [fetchJoke]);
return (
<div className="App">
<h1>Random Jokes</h1>
<p>{joke}</p>
<button onClick={fetchJoke}>Click for a random joke</button>
</div>
);
}
You can't conditionally call React hooks, like in the onClick handler of the button, as this breaks the rules of hooks. I suggest refactoring the useRandomJoke hook to return the fetched joke and a function to fetch the next random joke. You also shouldn't mix async/await with Promise chains as this is an anti-pattern.
const useRandomJoke = () => {
const [jokes, setJokes] = useState(null);
const jokeFetch = async () => {
const res = await fetch("https://api.icndb.com/jokes/random");
const data = await res.json();
setJokes(data.value.joke)
};
return [jokes, jokeFetch];
};
Then use the hook in the app.
function App() {
const [joke, getJoke] = useRandomJoke();
return (
<div className="App">
<h1>Random Jokes</h1>
<p>{joke}</p>
<button onClick={getJoke}>Click for Joke</button>
</div>
);
}
Well, there is more than one point to talk about here:
1- in React.js, you can only call custom hooks at the top level of your function's body (react recognizes any function starting with the keyword use as a hook)
function App() {
// top level is here
const randomJokes = useRandomJoke()
const [jokes, setJokes] = useState();
return (
<div className="App">
<h1>Random Jokes</h1>
<p>{jokes}</p>
<button onClick={()=>{setJokes(useRandomJoke)}}>
Click for Jokes
</button>
</div>
); }
export default App;
2- In your example I understand you want to have a new joke each time onClick triggers, in order to do so, I don't think using a custom hook is the ideal solution here, since your custom hook runs the fetchJokes method only once on initial render (as you described in your useEffect hook), I understand a lot of people mention that useEffect is the place to make API calls, but it doesn't necessarily applies to all use cases, in your example it is simple, you don't have to use useEffect neither create a custom hook.
a possible simple solution:
function App() {
// we always call hooks at the top level of our function
const [jokes, setJokes] = useState();
const fetchNewJoke = () => {
fetch("https://api.icndb.com/jokes/random")
//we'll run 2 "then"
.then(
// this will give us response and will return inform of
res.json
(res) => res.json()
) //.json is a format
.then((data) => {
setJokes(data.value.joke);
}); // now calling data from te returned values in res.json
};
};
return (
<div className="App">
<h1>Random Jokes</h1>
<p>{jokes}</p>
<button onClick={fetchNewJoke}>Click for Joke</button>
</div>
);
} export default App;
I am trying to add a loading screen whenever a URL change detect, So I am trying to put this code inside my _app.js file.
import Router from "next/router";
export default function App({ Component, pageProps }) {
const [loading, setLoading] = React.useState(false);
React.useEffect(() => {
const start = () => {
console.log("start");
setLoading(true);
};
const end = () => {
console.log("findished");
setLoading(false);
};
Router.events.on("routeChangeStart", start);
Router.events.on("routeChangeComplete", end);
Router.events.on("routeChangeError", end);
return () => {
Router.events.off("routeChangeStart", start);
Router.events.off("routeChangeComplete", end);
Router.events.off("routeChangeError", end);
};
}, []);
return (
<>
{loading ? (
<h1>Loading...</h1>
) : (
<Component {...pageProps} />
)}
</>
);
}
But the issue is I am not able to attact redux.
My current code with Redux is this :
import React, { useEffect } from "react"
import { wrapper } from "../redux/store"
import Layout from '../components/Layout';
import '../styles/globals.css'
import '../styles/media.css'
const MyApp = ({ Component, pageProps }) =>(
<Layout>
<Component {...pageProps} />
</Layout>
);
export default wrapper.withRedux(MyApp);
Can someone help me?
//Loading Component
const Loading = ()=>{
return (
<div> Loading gif here </div>
)
}
const App = ()=>{
const [currentPathname, setCurrentPathname] = useState<string>('');
const router = useRouter();
const [loading, setLoading] = useState<boolean>(false);
useEffect(() => {
if (router.isReady) {
if (router.pathname !== currentPathname) {
setLoading(true);
setCurrentPathname(router.pathname);
setTimeout(() => {
setLoading(false);
}, 3000);
}
}
}, [router, router.pathname]);
return (
<Layout>
{loading && <Loading />}
<Component {...pageProps} />
</Layout>
)
}
I assume that you have the loading component with some sort of loading gif.
I just check this solution inside my next app. Inside the useEffect, just check if the current path name is not the same then set the loading state to true to enable the loading component to show. Once it is enabled, set the current path name inside the local state and use a set timeout function to stop the loading after few seconds. In example, you will notice that I'm changing the loading state after 3 seconds
I am having a weird issue inside useEffect() in my React component. I have to make 2 separate axios requests to get data when the page loads. I am trying to use a hook variable to see if the data objects are populated before passing them to the JSX. Here's my current configuration:
import React, { useState, useEffect } from 'react';
import Navbar from '../components/layout/Navbar';
import ContactsCard from '../components/layout/ContactsCard';
import EmailCard from '../components/layout/EmailCard';
import MeetingsCard from '../components/layout/MeetingsCard';
import { useParams } from "react-router-dom";
import config from './../config/config';
import axios from "axios";
function SummaryPageNew() {
let { selectName } = useParams();
const [contactData, setContactData] = useState();
const [meetingData, setMeetingData] = useState();
const [loadingData, setLoadingData] = useState(true);
//API calls
async function getContactData() {
axios
.get(config.apiURL + `/affiliations/name/${selectName}`)
.then((response) => {
return setContactData(response.data[0]);
});
}
async function getMeetingData() {
axios
.get(config.apiURL + `/meetings_attendees/name/${selectName}`)
.then((response) => {
return setMeetingData(response.data);
});
}
useEffect((loadingData) => {
getContactData();
getMeetingData();
setLoadingData(false);
if (loadingData) {
//if the result is not ready so you make the axios call
getContactData();
getMeetingData();
setLoadingData(false);
}
}, []); // eslint-disable-line react-hooks/exhaustive-deps
return (
<div>
<Navbar />
<div>
<div style={{ textAlign: "center" }}>
<h3>Contact Information</h3>
<h5>Profile: {selectName}</h5>
</div>
{loadingData ? (
<p>Loading Please wait...</p>
) : (
<div className="row">
<ContactsCard contactData={contactData} />
<EmailCard emailData={meetingData} />
<MeetingsCard meetingData={meetingData} />
</div>
)}
</div>
</div>
)
}
export default SummaryPageNew
I have tried moving the setLoadingData(false) method inside the axios calls. If I move it inside the getMeetingData() call. This works ... sometimes. Apparently, on some occasions, it loads first and then the contactData doesn't get returned. In the current configuration, the DOM renders with "Loading Please wait...". What am I doing wrong here? How can I resolve this issue?
There are many issues with your code.
useEffect functions don't take any parameters. Your declaration of loadingData as a parameter is covering the actual loadingData variable in your component, and React will not pass a value for this.
You're missing a dependency on loadingData in your call to useEffect. As is, the function will only execute once and then never again as long as the component stays mounted. So, loadingData never gets set to false. Generally, it is a bad idea to avoid warnings about useEffect dependencies unless you have a very good reason.
My recommended solution would be to avoid storing extra state for the "loading" status. Instead, I would just check whether the two state values have been populated yet, and show the "Loading..." text if either is not.
This leaves you with:
function SummaryPageNew() {
let { selectName } = useParams();
const [contactData, setContactData] = useState();
const [meetingData, setMeetingData] = useState();
const isReady = contactData !== undefined && meetingData !== undefined;
//API calls
async function getContactData() { ... }
async function getMeetingData() { ... }
useEffect((loadingData) => {
getContactData();
getMeetingData();
}, []);
return (
<div>
<Navbar />
<div>
<div style={{ textAlign: "center" }}>
<h3>Contact Information</h3>
<h5>Profile: {selectName}</h5>
</div>
{isReady ? (
<div className="row">
<ContactsCard contactData={contactData} />
<EmailCard emailData={meetingData} />
<MeetingsCard meetingData={meetingData} />
</div>
) : (
<p>Loading Please wait...</p>
)}
</div>
</div>
)
}
react-query is a very powerful library for fetching data asynchronously using hooks. This avoids having to manage complex state which can easily fall out of sync. However, I'd learn the fundamentals of react hooks first!
You're dealing with async function calls. Javascript doesn't wait for your async functions to complete before it continues with your program. This means your calls are probably still fetching, while you already set loadingData to false. You can fix this by using Promise.all to get a callback when the async functions resolve:
//API calls
async function getContactData() {
return axios
.get(config.apiURL + `/affiliations/name/${selectName}`)
.then((response) => {
return setContactData(response.data[0]);
});
}
async function getMeetingData() {
return axios
.get(config.apiURL + `/meetings_attendees/name/${selectName}`)
.then((response) => {
return setMeetingData(response.data);
});
}
useEffect(() => {
let mounted = true
return () => { mounted = false }
Promise.all([getContactData(), getMeetingData()]).then(() => {
if (mounted) setLoadingData(false)
})
}, []); // eslint-disable-line react-hooks/exhaustive-deps
Also note the let mounted = true I've added: you want to make sure this component still exists whenever your async calls complete. If the calls take a while, it's not unthinkable you might have navigated away, for instance.
Finally, it's not a wise idea to disable react-hooks/exhaustive-deps. With a few changes you can setup your code in such a way that this ignore is no longer needed.
React want you to provide getContactData, getMeetingData in the dependency array. You can fix that by moving the data fetching function outside of you component. This means they no longer have access to the selectName variable, but you can provide that variable as an argument:
function SummaryPageNew() {
let { selectName } = useParams();
const [contactData, setContactData] = useState();
const [meetingData, setMeetingData] = useState();
const [loadingData, setLoadingData] = useState(true);
//API calls
useEffect(() => {
let mounted = true
Promise.all([
getContactData({ selectName }),
getMeetingData({ selectName })
]).then(([contactData, meetingData]) => {
if (!mounted) return
setContactData(contactData)
setMeetingData(meetingData)
setLoadingData(false)
})
return () => { mounted = false }
}, [selectName]);
return () // Render your component
}
async function getContactData({ selectName }) {
return axios
.get(config.apiURL + `/affiliations/name/${selectName}`)
.then((response) => {
return setContactData(response.data[0]);
});
}
async function getMeetingData({ selectName }) {
return axios
.get(config.apiURL + `/meetings_attendees/name/${selectName}`)
.then((response) => {
return setMeetingData(response.data);
});
}
I use AppContext, when I fetch data from server I want it to save in context but on the first render it doesn't save. If I make something to rerender state data appears in context.
Here is my code:
useEffect(() => {
fetch('https://beautiful-places.ru/api/places')
.then((response) => response.json())
.then((json) => myContext.updatePlaces(json))
.then(() => console.log('jsonData', myContext.getPlaces()))
.catch((error) => console.error(error));
}, []);
My getPlaces and updatePlaces methods:
const [allPlaces, setAllPlaces] = useState();
const getPlaces = () => {
return allPlaces;
};
const updatePlaces = (json) => {
setAllPlaces(json);
};
const placesSettings = {
getPlaces,
updatePlaces,
};
Here is how I use AppContext:
<AppContext.Provider value={placesSettings}>
<ThemeProvider>
<LoadAssets {...{ assets }}>
<SafeAreaProvider>
<AppStack.Navigator headerMode="none">
<AppStack.Screen
name="Authentication"
component={AuthenticationNavigator}
/>
<AppStack.Screen name="Home" component={HomeNavigator} />
</AppStack.Navigator>
</SafeAreaProvider>
</LoadAssets>
</ThemeProvider>
</AppContext.Provider>;
Could you explain please why my console.log('jsonData', ...) returns undefined?
I don't understand because on previous .then I saved it.
Edit to note that the code below is not copy-paste ready. It is an example of how to attack the problem – you will need to implement it properly in your project.
The 'problem' is that hooks are asynchronous – in this specific case, your useEffect further uses an asynchronous fetch too.
This means that the data that is returned by the fetch will only be available after the component has rendered, and because you're not updating state/context using a hook, the context won't update.
The way to do this requires a few changes.
In your context implementation, you should have a setter method that sets a state variable, and your getter should be that state variable.
placesContext.js
import React, { createContext, useState } from "react";
export const placesContext = createContext({
setPlaces: () => {},
places: [],
});
const { Provider } = placesContext;
export const PlacesProvider = ({ children }) => {
const [currentPlaces, setCurrentPlaces] = useState(unit);
const setPlaces = (places) => {
setCurrentPlaces(places);
};
return (
<Provider value={{ places: currentPlaces, setPlaces }}>{children}</Provider>
);
};
Wrap your App with the created Provider
App.js
import { PlacesProvider } from "../path/to/placesContext.js";
const App = () => {
// ...
return (
<PlacesProvider>
// Other providers, and your app Navigator
</PlacesProvider>
);
}
Then, you should use those variables directly from context.
MyComponent.js
import { placesContext } from "../path/to/placesContext.js";
export const MyComponent = () => {
const { currentPlaces, setPlaces } = useContext(placesContext);
const [hasLoaded, setHasLoaded] = useState(false);
useEffect(() => {
async function fetchPlacesData() {
const placesData = await fetch('https://beautiful-places.ru/api/places');
if (placesData) {
setPlaces(placesData);
} else {
// error
}
setHasLoaded(true);
}
!hasLoaded && fetchPlacesData();
}, [hasLoaded]);
return (
<div>{JSON.stringify(currentPlaces)}</div>
)
};