How to use onSuccess with useQueries in react query ?

In React Query, useQuery is a powerful hook that not only helps us asynchronously fetch data but also handles caching, retries, and data updates. onSuccess is an option of useQuery that is triggered when the request succeeds. We can leverage onSuccess to perform various tasks, such as triggering notifications after data retrieval, executing post-processing on data, or updating the state of other components.

Usage:

javascript
import { useQuery } from 'react-query';

function fetchProjects() {
  return fetch('/api/projects').then(res => res.json());
}

function MyApp() {
  const { data, isError, error } = useQuery('projects', fetchProjects, {
    onSuccess: (data) => {
      console.log('Data request succeeded; here is the retrieved data:', data);
      // Perform tasks such as data transformation, triggering notifications, or updating other component states
    }
  });

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

  return (
    <div>
      {data.map(project => (
        <p key={project.id}>{project.name}</p>
      ))}
    </div>
  );
}

Example Explanation:

In the above code, we define the fetchProjects function to fetch data and pass it to useQuery. In the third parameter of useQuery, we set the onSuccess callback function. Whenever fetchProjects successfully fetches data, onSuccess is executed. Within this callback, we can perform tasks such as logging, data formatting, or state updates.

Advanced Applications:

We can also use onSuccess to trigger updates or resets for other queries. For example, suppose we have a query for a project list and a query for project details. When a user adds a new project, we might want to refetch the project list to ensure the list data is up-to-date. This can be achieved using QueryClient:

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

function useAddProject() {
  const queryClient = useQueryClient();

  const addProject = (newProject) => {
    return fetch('/api/projects', {
      method: 'POST',
      body: JSON.stringify(newProject),
    }).then(res => {
      // After adding a project, refetch the project list
      queryClient.invalidateQueries('projects');
    });
  };

  return addProject;
}

In this example, whenever a new project is added, we call the invalidateQueries method to mark the query named projects as invalid. React Query will then refetch the project list to ensure the user sees the latest data.

Summary:

onSuccess provides a very useful interface in React Query, allowing us to execute specific operations after a data request succeeds, thereby enhancing the interactivity and user experience of the application. By combining methods from QueryClient, we can easily implement dependencies and updates between data, making data state management more efficient and concise.