What is React Query useMutation?

React Query is a popular library in the React community. It’s known for its efficient and intuitive approach to server state management.

While many are familiar with its querying capabilities, React Query also offers tools for handling mutations - changes to your server data. One such tool is the useMutation hook. In this post, we'll delve into the workings of useMutation and talk about why it’s important.

What is React Query useMutation?

useMutation is a hook provided by React Query that helps you handle server-side mutations like POST, PUT, DELETE requests, etc. Beyond just making the request, it provides out-of-the-box functionalities for managing local UI state, handling optimistic updates, and even retrying failed mutations.

How useMutation differs from traditional approaches

While React’s built-in hooks like useState and useEffect can be used to handle server state, useMutation abstracts away a lot of the complexities. Unlike traditional methods which require manual management of loading states, error states, and cache updates, useMutation provides these features out-of-the-box, which leads to cleaner code that’s easier to maintain.

How to implement React Query useMutation

Setting up a mutation in React Query is quite simple. Here's a basic example:

import { useMutation } from 'react-query';

function MyComponent() {
  const mutation = useMutation(newData => fetchData('/api/data', {
    method: 'POST',
    body: JSON.stringify(newData),
  }));

  return (
    <button onClick={() => mutation.mutate({ id: 1, name: 'New Data' })}>
      Add New Data
    </button>
  );
}

In the above example, when the button is clicked, a POST request is made to /api/data.

Feedback and UI states

One significant advantage of React Query useMutation is the immediate feedback on the mutation's status. It provides status flags like isLoading, isError, and data that can be used to update the UI accordingly.

if (mutation.isLoading) return 'Submitting...';
if (mutation.isError) return 'An error occurred';
if (mutation.isSuccess) return `Data added: ${mutation.data.name}`;

Optimistic updates

To make apps feel faster, it's a common practice to update the UI optimistically before a server response is received. useMutation makes this straightforward with the onMutate and onError callbacks.

const mutation = useMutation(
  newData => fetchData('/api/data', {
    method: 'POST',
    body: JSON.stringify(newData),
  }),
  {
    onMutate: (newData) => {
      // Optimistically update the UI here
    },
    onError: (error, newData, context) => {
      // Rollback the optimistic update in case of an error
    }
  }
);

Invalidating and refetching after mutation

React Query allows seamless integration between queries and mutations. After a successful mutation, you often want to refetch some queries to keep the data in sync. Using the previously discussed invalidateQueries, this is pretty easy to do:

const mutation = useMutation(
  newData => fetchData('/api/data', {
    method: 'POST',
    body: JSON.stringify(newData),
  }),
  {
    onSuccess: () => {
      queryClient.invalidateQueries('myQueryKey');
    }
  }
);

Retrying mutations

Occasionally, mutations might fail due to transient issues such as network hiccups or temporary server problems. useMutation provides a retry mechanism to elegantly handle these scenarios:

const mutation = useMutation(
  newData => fetchData('/api/data', {
    method: 'POST',
    body: JSON.stringify(newData),
  }),
  {
    retry: 3, // This will retry the mutation up to 3 times if it fails
  }
);

Conclusion

The React Query useMutation hook is a great way to manage server-side mutations. From handling the actual request, providing feedback, enabling optimistic updates, to integrating seamlessly with queries, useMutation wraps everything up in a neat package.

If you use it properly, you should be able to boost the user experience and robustness of your React apps.