How can I implement optimistic updates in my React app using React Query?

How can I implement optimistic updates in my React app using React Query?

To implement optimistic updates with React Query, you can use the onMutate callback in your mutation. This allows you to update the UI immediately before the mutation is confirmed.

Can you give me a code example of that?

Sure! Here's a simple example:

const mutation = useMutation(mutateFunction, {
  onMutate: async (newData) => {
    await queryClient.cancelQueries('data');
    const previousData = queryClient.getQueryData('data');
    queryClient.setQueryData('data', old => [...old, newData]);
    return { previousData };
  },
  onError: (err, newData, context) => {
    queryClient.setQueryData('data', context.previousData);
  },
});

This code updates the data optimistically before the mutation completes.

What happens if the mutation fails?

If the mutation fails, you can use the onError callback to revert the optimistic update by restoring the previous data using the context returned from onMutate.

Are there any best practices for using optimistic updates?

Yes, some best practices include keeping the optimistic update simple, ensuring the UI reflects the expected state, and handling errors gracefully to maintain a good user experience.