After installing the React query library package in your React project, follow these steps to implement its functionalities in your app.

Step 1: Creating a Query Client

The QueryClient is the heart of React Query. It acts as a central hub, managing the cache, fetching data, and updating your components. To use React Query, you need to create an instance of QueryClient and make it available throughout your application:

import { QueryClient, QueryClientProvider } from 'react-query';

const queryClient = new QueryClient();

const App = () => (
  <QueryClientProvider client={queryClient}>
    <MyComponent />
  </QueryClientProvider>
);

Note: To use React Query, we must wrap our application in a QueryClientProvider.

This is essential as it makes the React Query functionalities available throughout your app, allowing them to leverage the power of React Query for data fetching.

Step 2: Fetching Data with useQuery

The useQuery hook is fundamental to React Query, providing an elegant and efficient way to fetch data from a server. Let's break down how it works:

Structure of useQuery

The useQuery hook accepts two main arguments:

• Query Key: A unique identifier for your query, typically an array ['posts'] or ['post', postId]. This key helps React Query identify and cache your data.
• Query Function: An asynchronous function that returns a promise, responsible for actually fetching the data from your server.

Here's how you would use useQuery to fetch a list of posts:

import { useQuery } from 'react-query';

function PostList() {
  // Define the query key
  const queryKey = ['posts']; 

  // Define the query function to fetch posts
  const fetchPosts = async () => {
    const response = await fetch('https://jsonplaceholder.typicode.com/posts');
    return response.json();
  };

  // Use the useQuery hook
  const { isLoading, isError, data, error } = useQuery(queryKey, fetchPosts);

  // Handle loading state
  if (isLoading) {
    return <div>Loading posts...</div>;
  }

  // Handle error state
  if (isError) {
    return <div>Error: {error.message}</div>;
  }

  // Render the post list
  return (
    <ul>
      {data.map(post => (
        <li key={post.id}>{post.title}</li>
      ))}
    </ul>
  );
}

In this example:

• We define a queryKey as ['posts'] to uniquely identify this data.
• The fetchPosts function fetches data from an API endpoint.
• useQuery returns several values like isLoading, isError, data, and error to handle different states of the query.
• We conditionally render different parts of the component based on the state of the query: loading, error, or success.

Advantages of using useQuery

There are benefits of utilizing the useQuery hook of react query and they are:

• Automatic Caching: React Query automatically caches the query results based on the queryKey. If you re-fetch the same data within the cache's lifespan, it retrieves it from the cache, reducing network requests and improving performance.
• Background Updates: React Query can automatically refetch data in the background when the window regains focus or after a specified interval. This ensures your data stays up-to-date without manual intervention.
• Built-in State Management: With useQuery, you don't need to manually manage loading states or errors. The hook provides this information out of the box, making your components cleaner and more readable.