How to re-fetch single items of a collection in react- query

In React Query, refetching a single item from a collection can be achieved in several ways, depending on how you configure your queries and data dependencies. Below, I will explain two common methods:

Method 1: Using queryClient.invalidateQueries

react-query provides a queryClient instance that can be used to directly control the state of queries. When you need to refetch a single item from a collection, you can use the queryClient.invalidateQueries method to invalidate the cache for a specific query, thereby triggering a refetch.

Suppose we have a query that fetches a user list, where each user has a unique ID, and we need to update the data for a specific user.

jsx
import { useQuery, useQueryClient } from 'react-query';

function useUsers() {
  return useQuery('users', fetchUsers);
}

function UserComponent({ userId }) {
  const queryClient = useQueryClient();
  const { data: users } = useUsers();

  const refetchUser = async () => {
    // Invalidate the query for a specific user
    await queryClient.invalidateQueries(['users', userId], {
      refetchActive: true, // Refetch queries in active state
      refetchInactive: false, // Do not refetch queries in inactive state
    });
  };

  return (
    <div>
      {users?.map(user => (
        <div key={user.id}>{user.name}</div>
      ))}
      <button onClick={refetchUser}>Refetch User</button>
    </div>
  );
}

In this example, we invalidate the query for a specific user and refetch it by calling the refetchUser function.

Method 2: Using queryClient.fetchQuery

If you need to precisely control the refetch process or if you want to fetch data independently without affecting other components, you can use queryClient.fetchQuery.

jsx
function UserComponent({ userId }) {
  const queryClient = useQueryClient();

  const fetchUser = async () => {
    const user = await queryClient.fetchQuery(['user', userId], () => fetchUserById(userId));
    // Optionally: update the query cache
    queryClient.setQueryData(['user', userId], user);
  };

  return (
    <button onClick={fetchUser}>Fetch User</button>
  );
}

In this example, the fetchUser function fetches the latest user data directly from the server and optionally updates the query cache.

Summary

Both methods can be effectively used to refetch a single item from a collection in React Query. The choice of method depends on your specific needs, such as whether you need the changes to immediately reflect in the UI or if you need to decouple from other data queries. In practice, you may need to adjust the data fetching and cache update strategies based on specific circumstances.