How to handle server-side errors using react-query and formik?

In using React Query and Formik, handling server-side errors is a common requirement. This typically involves two scenarios: one is when using React Query for data fetching and mutation, and the other is when submitting forms with Formik. Below are strategies and examples for handling server-side errors in both cases.

1. Handling Server-Side Errors in React Query

Strategy:

• When using useQuery or useMutation from React Query, you can handle errors using the onError callback.
• Displaying error messages is typically achieved through state management, such as setting an error state and displaying it in the component.

Example:

Suppose we use React Query to send a POST request and handle potential server-side errors.

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

function submitData(data) {
  return fetch('/api/data', {
    method: 'POST',
    body: JSON.stringify(data),
    headers: {
      'Content-Type': 'application/json',
    },
  }).then(res => {
    if (!res.ok) {
      throw new Error('Server responded with an error!');
    }
    return res.json();
  });
}

function MyComponent() {
  const { mutate, isError, error } = useMutation(submitData, {
    onError: (err) => {
      // Handle errors, such as displaying notifications or logging
      console.error('Error submitting data:', err.message);
    },
  });

  const handleSubmit = (data) => {
    mutate(data);
  };

  return (
    <div>
      {isError && <p>Error: {error.message}</p>}
      <button onClick={() => handleSubmit({ name: 'John' })}>Submit</button>
    </div>
  );
}

2. Handling Server-Side Errors in Formik

Strategy:

• In Formik's onSubmit function, if the request fails, you can use Formik's setErrors method to set form errors.
• Typically, error messages need to be parsed from the server response and set to the corresponding form fields.

Example:

Suppose we have a form managed by Formik that requires handling server-side error messages upon submission.

javascript
import { Formik, Form, Field, ErrorMessage } from 'formik';

function MyForm() {
  const handleSubmit = (values, { setSubmitting, setErrors }) => {
    fetch('/api/form-submit', {
      method: 'POST',
      body: JSON.stringify(values),
      headers: {
        'Content-Type': 'application/json',
      },
    })
    .then(res => res.json())
    .then(data => {
      if (data.error) {
        setErrors({ submit: data.message });
      }
      setSubmitting(false);
    })
    .catch(error => {
      setErrors({ submit: 'An unexpected error occurred' });
      setSubmitting(false);
    });
  };

  return (
    <Formik
      initialValues={{ email: '' }}
      onSubmit={handleSubmit}
    >
      {({ isSubmitting }) => (
        <Form>
          <Field type="email" name="email" />
          <ErrorMessage name="email" component="div" />
          <button type="submit" disabled={isSubmitting}>
            Submit
          </button>
        </Form>
      )}
    </Formik>
  );
}

In this example, if the server response contains error information (e.g., the submitted email already exists), we set this error message to Formik's error state, allowing it to be displayed to the user in the form.

Summary

Combining React Query and Formik for handling server-side errors involves multiple aspects such as error handling, state updates, and user feedback. By effectively utilizing the APIs and features provided by both, you can manage and provide feedback on server-side errors, enhancing user experience and application robustness.