Tutorial of queryClient in React Client Component with Example

React | how-to |

Working with data-fetching libraries in React has brought React Query to the top, making state management and data fetching easier and more modern. Among all the elements of React Query, one important component is QueryClient. In this article, we are going to dive into what a QueryClient is, what uses it holds, and how you can effectively manage your data using it. We will also look into such important functions as setQueryData and getQueryData to see how they play such a vital role in adding an extra layer of effectiveness to the data experience inside a React application.

What is a QueryClient?

A QueryClient is the core of React Query. It’s, in short, a class that controls caching and synchronizing server states. It’s a kind of smart manager of your data, knowing what you have, where it comes from, and how to update it. You do not need to manage the loading state or cache the response using React Query. The QueryClient handles all of this for you, allowing you to focus on building your application.

Why Use a QueryClient?

Using a QueryClient brings several benefits to your React application:

  1. Automatic Caching: QueryClient automatically caches your data. This means that if you fetch the same data again, it can return the cached version instead of making another network request. This can greatly improve performance and reduce unnecessary load on your server.
  2. Synchronization: The QueryClient ensures that your data stays in sync with the server. If the data changes on the server, the QueryClient will automatically update your application to reflect these changes, reducing the chances of stale data.
  3. Easy Data Fetching: Instead of using traditional methods like fetch or axios throughout your components, QueryClient abstracts these calls into a simple API. This makes your components cleaner and easier to maintain.
  4. Optimistic Updates: When you update data, the QueryClient can optimistically update the UI before the server responds. This makes your app feel faster and more responsive to users.

Setting Up QueryClientProvider

To make the QueryClient available to your React application, you need to wrap your application with QueryClientProvider. This is typically done at a high level in your component tree, often in your index.js or App.js file.

Here’s how to do it:

import React from 'react';
import ReactDOM from 'react-dom';
import { QueryClient, QueryClientProvider } from 'react-query';
import App from './App';

const queryClient = new QueryClient();

ReactDOM.render(
  <QueryClientProvider client={queryClient}>
    <App />
  </QueryClientProvider>,
  document.getElementById('root')
);

In this example, we create a new instance of QueryClient and pass it to QueryClientProvider. Now, any component within App can access the QueryClient and use React Query hooks.

Using QueryClient: Core Functions

Once you have your QueryClient set up, you can start leveraging its powerful features. Two key methods you’ll often use are setQueryData and getQueryData. Let’s break these down.

What Does QueryClient Do?

The QueryClient manages multiple aspects of data fetching and state management. Here’s what it primarily does:

  • Caching: Stores the fetched data and retrieves it when needed without making new requests.
  • Updating: Manages updates to your data, allowing you to modify cached data using methods like setQueryData.
  • Refetching: Automatically refetches data when it becomes stale or based on specific conditions you define.
  • Synchronization: Keeps your client-side data in sync with the server state.

Getting Query Data with getQueryData

The getQueryData method allows you to retrieve cached data associated with a specific query key. This can be very useful for optimizing your application’s performance.

Here’s how to use it:

const data = queryClient.getQueryData('myQueryKey');
console.log(data);

In this example, we’re fetching the cached data associated with 'myQueryKey'. If the data is not available, getQueryData will return undefined. This is great for situations where you want to avoid making an unnecessary request.

Setting Query Data with setQueryData

The setQueryData method is where the magic happens. It allows you to update the cached data directly. This can be particularly useful in scenarios where you want to update your UI optimistically.

Here’s a quick example:

queryClient.setQueryData('myQueryKey', oldData => {
  return { ...oldData, newField: 'newValue' };
});

In this case, we’re updating the cached data associated with 'myQueryKey'. The callback function receives the old data and returns a new version of it, which is then stored in the cache. This is super handy for form submissions or any updates where you want the UI to reflect changes immediately.

Real-World Use Cases

Understanding how to use QueryClient is crucial, but seeing it in action makes it even clearer. Let’s look at some practical scenarios where you might leverage the QueryClient.

Example: Fetching Data on Component Mount

Imagine you have a component that needs to fetch user data when it mounts. With React Query, this can be easily achieved with the useQuery hook, which utilizes the QueryClient under the hood.

import { useQuery } from 'react-query';

const UserProfile = () => {
  const { data, isLoading, error } = useQuery('userData', fetchUserData);

  if (isLoading) return <div>Loading...</div>;
  if (error) return <div>Error: {error.message}</div>;

  return (
    <div>
      <h1>{data.name}</h1>
      <p>{data.email}</p>
    </div>
  );
};

In this example, when UserProfile mounts, it fetches user data. The QueryClient caches this data, so if the component remounts or if you navigate away and then back again, React Query can quickly provide the cached data without hitting the network.

Example: Updating Data

Suppose you have a form where users can update their profile. You can use setQueryData it to optimistically update the cached data while you await a server response.

const updateUserData = async (newData) => {
  await fetch('/api/user', {
    method: 'PUT',
    body: JSON.stringify(newData),
  });
};

const UserProfile = () => {
  const queryClient = useQueryClient();
  const { data } = useQuery('userData', fetchUserData);

  const handleSubmit = async (newData) => {
    queryClient.setQueryData('userData', newData);
    await updateUserData(newData);
  };

  return (
    <form onSubmit={handleSubmit}>
      {/* form fields for user data */}
    </form>
  );
};

In this code, when the form is submitted, setQueryData updates the cached user data immediately. This means the UI reflects the changes instantly, making for a snappy user experience.

Performance Optimization

QueryClient can significantly improve the performance of your React application. For instance, by reducing the number of network requests through caching, your application becomes more responsive. Additionally, the automatic refetching mechanism ensures that users always see the most up-to-date information without the need for manual refreshes.

Handling Multiple Queries

If your application fetches multiple pieces of data, managing them with QueryClient becomes even more powerful. You can define several queries and keep your component tree clean.

const App = () => {
  const { data: users } = useQuery('users', fetchUsers);
  const { data: posts } = useQuery('posts', fetchPosts);

  return (
    <div>
      <h2>Users</h2>
      {users.map(user => <User key={user.id} user={user} />)}

      <h2>Posts</h2>
      {posts.map(post => <Post key={post.id} post={post} />)}
    </div>
  );
};

In this example, you can fetch users and posts independently while maintaining a clean and organized structure. React Query ensures that each query’s state is isolated, so they don’t interfere with one another. If you want to know more about code quality, check out this clean code article.

Error Handling in Queries

One of the best practices when using React Query is handling errors gracefully. The QueryClient helps with this as well. You can access the error state through the query’s status and display meaningful messages to users.

const { data, error } = useQuery('userData', fetchUserData);

if (error) {
  return <div>An error occurred: {error.message}</div>;
}

In this way, you can improve the user experience by providing feedback when things go wrong.

Conclusion

Using a QueryClient in your React application opens you up to endless possibilities for managing data effectively. Automatic caching and synchronization, plus easy-to-use methods such as setQueryData and getQueryData, help make your users’ experience seem seamless.

It has become a very popular choice for many developers because it takes care of all the heavy lifting associated with data fetching. Through the power of QueryClient, you can focus on building rich user interfaces without getting bogged down by state management complexities.

In case you start building applications soon, consider adding React Query and QueryClient to the bag. You’ll be astonished at how much silken your data interactions turn out to be and your users will appreciate the responsiveness of an application.

Related Posts

Scroll to Top