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React Query

Data Fetching Libraries​

  • Using hte useState and useEffect hooks is good way to learn basics of data fetching in React components.
  • There are good React libraries available for data fetching, for example:
  • These libraries provides nice features like caching, error handling, detect out-of-date data etc. and it is recommended to use these when developing proper React apps.

React Query (Tanstack Query)​

  • To install React Query , execute the following npm command in your project using the command line.
npm install @tanstack/react-query
  • First, you have to create a client instance and provide it to your app using the QueryClientProvider component. Query client is responsible for data caching and you can use it to configure global settings for React Query.
import { QueryClient QueryClientProvider } from '@tanstack/react-query'

// Create a client
const queryClient = new QueryClient()

function App() {
  return (
    // Provide the client to your App
    <QueryClientProvider client={queryClient}>
      <YourApp />
    </QueryClientProvider>
  )
}

GET request​

  • You can use useQuery hook function to send GET request
  • The syntax is the following
useQuery({ queryKey: ['your_query_key'], queryFn: fetchSomething })

where

  • queryKey is the unique key for the query
  • queryFn is the function that invokes the query. The function must return a promise.
import { useQuery } from '@tanstack/react-query'

function YourComponent() {
  const result = useQuery({
    queryKey: ['cars'], 
    queryFn: () =>  
      fetch('https://cars.com/cars').then(res => res.json())
  })
}
  • The query result is an object that contains the following boolean properties:
    • isLoading, isSuccess, isError
  • If the request succeed, you can access the data using the data property (state is not needed to store response data).
  • The request is done when the component is rendered first time, therefore you don't need useEffect hook.
import { useQuery } from '@tanstack/react-query'

function YourComponent() {
  const {isLoading, isSuccess, data} = useQuery({
    queryKey: ['cars'], 
    queryFn: () => fecthCars
  })

  if (isLoading) {
    return <span>Loading...</span>
  }

  return (
    <ul>
      {data.map((car) => (
        <li key={car.id}>{car.brand}</li>
      ))}
    </ul>
  )
  • It is also a good practice to split your REST call functions to own module
// services.js
export async function fetchCars() {
  const response = await fetch(API_URL);
  return await response.json();
}
  • Then, you can import these in your components
import { useQuery } from '@tanstack/react-query';
import { fetchCars } from './services.js`;

function YourComponent() {
  const { isLoading, isSuccess, data } = useQuery({
    queryKey: ['cars'], 
    queryFn: () => fecthCars
  })
}

React query refetch data automatically when:

  • The window is refocused
  • The network is reconnected
  • New instance of query is mounted
  • You have configured optional refetch interval

By default, React Query considers data to be stale (out of date) immediately after a successful query, which means that it will automatically trigger a background refetch the next time the data is accessed. However, you can customize this behavior by setting a specific stale time for your queries using the staleTime option.

POST, DELETE & UPDATE​

  • You can use useMutation hook to update date
import { useMutation } from '@tanstack/react-query';

const { mutate } = useMutation(deleteCar, {
    onSuccess: () => {
      // Car deleted
    },
    onError: () => {
      // Error in deletion
    },
  });
  • Then you can call mutate
<button onClick={() => mutate(carid)}>Delete<button>
  • The useQueryClient hook can be used to handle cache. Query client provides invalidateQueries function that can be used to invalidate queries and force to refetch data.
  const queryClient = useQueryClient();

  const { mutate } = useMutation(deleteCar, {
    onSuccess: () => {
      // Clears the cache and refetch data
      queryClient.invalidateQueries(["cars"]);
    },
    onError: () => {
      alert("There was an error");
    },
  });

  • Now, the cars query is refetched after the successful mutation.

Further reading​