Conditional Query with React Query

A common scenario in React Query involves conditionally running a query based on certain conditions, such as user authentication, feature availability, or other logical requirements. This guide demonstrates how to implement conditional queries with React Query effectively.

What are conditional queries in React Query?

Conditional queries are those that only run under specific conditions. For example, you might want to fetch user data only if a user is logged in. React Query's useQuery hook makes implementing this pattern straightforward, thanks to its enabled option. This option accepts a boolean that determines whether the query should run.

How to implement a conditional query?

Here's how to use the enabled option to control the execution of a query:

import { useQuery } from 'react-query';

function UserProfile({ userId }) {
  const { data, isLoading, error } = useQuery(
    ['userProfile', userId],
    () => fetchUserProfile(userId),
    {
      enabled: !!userId, // Query runs only if userId is truthy
    }
  );

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

  return (
    <div>
      <h2>User Profile</h2>
      {/* Render user data */}
    </div>
  );
}

async function fetchUserProfile(userId) {
  const response = await fetch(`/api/user/${userId}`);
  if (!response.ok) {
    throw new Error('Network response was not ok');
  }
  return response.json();
}

In this example, the useQuery hook fetches a user profile from an API. The query is only executed if userId is truthy, thanks to the enabled option. This prevents unnecessary API calls and ensures that your component logic remains clean and efficient.

Best practices for conditional queries

• Validate conditions early: Check the conditions required for your query to run as early as possible. This approach helps in avoiding unnecessary computation or state updates.
• Leverage dependencies: React Query's dependency array in the useQuery hook ensures that your query reruns when dependencies change. Use this feature to automatically refetch data when conditions change.
• Manage loading and error states: Even with conditional queries, handling loading and error states is crucial for a smooth user experience. Ensure you render appropriate UI feedback based on the query's state.

Conditional queries in React Query offer a powerful way to optimize data fetching based on runtime conditions. By using the enabled option and following best practices, you can build more efficient and user-friendly React applications.