How to set custom error message React Query

When using React Query, setting custom error messages typically involves using try...catch statements to capture errors and handling them through Error Boundaries, state management, or other logic.

For example, suppose we are using the useQuery hook in React Query to fetch data from an API. We can use try...catch within the request function to capture and handle errors, then return different error messages based on the error type. Here is a simple example:

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

const fetchUserData = async () => {
  try {
    const response = await fetch('https://someapi/user/data');
    if (!response.ok) {
      throw new Error('Network request failed');
    }
    return response.json();
  } catch (error) {
    // Handle different types of errors
    if (error.response && error.response.status === 404) {
      throw new Error('User data not found');
    } else if (error.response && error.response.status === 500) {
      throw new Error('Server error');
    } else {
      throw new Error('Request failed');
    }
  }
}

function MyComponent() {
  const { data, error, isError } = useQuery('userData', fetchUserData);

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

  // Render data normally
  return <div>{data.name}</div>;
}

In the above code, the fetchUserData function attempts to fetch user data from an API. If the network request fails or the server returns an error status code, it throws a custom error message. These errors are handled by the useQuery hook and passed to the component via the error object. In the component, we check the isError state; if true, we render an error message showing the detailed cause.

This approach allows developers to provide more targeted user feedback based on different error scenarios, enhancing the user experience. When using React Query, customizing error messages is important because it helps provide more specific error information to end users, improving the user experience. React Query itself does not directly offer a specific API for setting custom error messages, but you can achieve this through error handling.

Basic Steps

1. Capture errors: In your query function, capture any errors that may be thrown.
2. Create custom errors: After capturing errors, generate custom error messages based on the error type or content.
3. Throw custom errors: Throw the custom error message.
4. Handle errors in the component: When using useQuery or similar hooks, retrieve these errors from the hook's returned state and display them to the user.

Example Code

Suppose you have an API call to fetch user information and you want to provide more specific error messages on failure:

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

// Simulated API request function
const fetchUserData = async (userId) => {
  try {
    const response = await fetch(`/api/users/${userId}`);
    if (!response.ok) {
      throw new Error('Network response was not ok');
    }
    return response.json();
  } catch (error) {
    // Capture errors and create custom error messages
    if (error.response?.status === 404) {
      throw new Error(`User with ID ${userId} not found.`);
    } else {
      throw new Error('Failed to fetch user data. Please try again later.');
    }
  }
};

function UserProfile({ userId }) {
  const { data, error, isLoading } = useQuery(['user', userId], () => fetchUserData(userId));

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

  return (
    <div>
      <h1>{data.name}</h1>
      <p>Email: {data.email}</p>
    </div>
  );
}

In this example, we first capture errors in the fetchUserData function. Based on the error type, we throw different custom error messages. Then, in the React component, we use the useQuery hook to call fetchUserData. This hook manages various states of the asynchronous request, including loading and error handling. If the request throws an error, we display the error message in the component.

By doing this, you can display more useful, customized error messages for different error scenarios, which can significantly enhance the user experience of the application.