Error Checking in Server Actions for React Applications

Implementing Error Checking in Server Actions for React Applications with useFormState

This article guides you through adding error checking to server actions in a React application. We'll leverage the `useFormState` hook to simplify state management and error handling. Clear explanations and examples will make the process easy to follow.

The Importance of Error Handling

Imagine you're building a to-do list app. Users should be able to add new tasks, but what happens if something goes wrong during creation? Error checking ensures a smooth user experience by gracefully handling unexpected issues like database errors or invalid data.

Introducing useFormState

`useFormState` is a powerful hook from React Hook Form that simplifies managing form state and handling form submissions. It provides a clean way to access form data, control submission, and update state based on the action's outcome (success or error).

Setting Up Try-Catch Blocks

Let's say we have a server action responsible for creating a new task. To catch potential errors, we'll wrap the core logic of this action within a `try-catch` block, similar to the previous approach.

try {
  // Code that interacts with the database (e.g., Prisma) to create a new task
} catch (error) {
  // Handle the error here, potentially by returning an object with an "error" message
}

Returning Informative Messages

Similar to before, Next.js might object to directly returning an error within the `catch` block. We can create an object to hold informative messages:

try {
  // Code that interacts with the database
} catch (error) {
  return { message: "Error creating task" };
}

Using useFormState

Now, we'll integrate `useFormState` into the `taskFormCustom` component:

1. Import the hook:

import { useFormState } from 'react-hook-form';

2. Initial State:

Define the initial state for the form. This state object might hold properties for the task title, description, etc.

const initialState = {
  title: "",
  description: "",
};

3. Invoke useFormState:

Call `useFormState` within your component, passing two arguments:

• **createTaskCustom:** This is the function reference to your server action that handles task creation.
• **initialState:** The initial state object defined earlier.

const { formState, formAction } = useFormState(createTaskCustom, initialState);

4. Access formState:

The `formState` object returned by `useFormState` provides access to the current state of the form, including potential error messages returned by the server action.

Displaying Error Messages

We can leverage `formState.message` to conditionally display error messages:

const message = formState.message; // Get the message from formState

if (message) {
  // Display an error paragraph with the message content
} else {
  // No message means success, so we don't need to display anything
}

useActionState Hook

The `useActionState` hook is a React hook that helps you manage state updates based on the result of a form action.

Availability

**Canary:** This hook is currently only available in React's experimental Canary channels. Learn more about release channels here.

**Framework Support:** For full functionality, you'll need a framework that supports React Server Components (RSC).

Functionality

Here's how `useActionState` works:

• State and Action:** It returns an array containing two values:
  • **Current state:** The current state of the form, which initially matches the provided `initialState`.
  • **Action function:** A function you can use to trigger form submission and update state based on the server's response.
• Server Interactions:** It allows you to handle server interactions triggered by form submissions. It can display the server's response even before hydration finishes in RSC.

Usage

The basic syntax of `useActionState` is:

const [state, formAction] = useActionState(fn, initialState, permalink?)

Testing Error Handling

Here's how we can test error handling:

1. Successful Creation: Create a new task and verify that no error message appears.
2. Introducing an Error: Modify the server action code to reference a non-existent model. This should trigger the error handling mechanism.
3. Error Display: Observe if the error message appears in the browser. If it does, our error handling is working correctly