Revalidation after mutations in Remix - Mini Project: Build & Apply

Revalidation after mutations in Remix

📖 Scenario: You are building a simple blog app using Remix. When a user adds a new post, the list of posts should update automatically without refreshing the whole page.

🎯 Goal: Create a Remix route that shows a list of posts. Add a form to create a new post. After submitting the form, the posts list should revalidate and show the new post.

📋 What You'll Learn

Create a posts array with initial posts

Add a config variable to control revalidation

Use Remix's useFetcher to submit new posts

Trigger revalidation of the posts list after mutation

💡 Why This Matters

🌍 Real World

This pattern is common in web apps where you want to update parts of the page after data changes without refreshing everything.

💼 Career

Understanding revalidation after mutations is important for building responsive, user-friendly web apps with Remix or similar frameworks.

1

Set up initial posts data

Create a variable called posts as an array with these exact objects: { id: 1, title: 'First Post' } and { id: 2, title: 'Second Post' }.

Remix

# Your code here

Hint

Use const posts = [ ... ] with two objects inside.

2

Add a revalidation config variable

Create a constant called shouldRevalidate and set it to true.

Remix

const posts = [
  { id: 1, title: 'First Post' },
  { id: 2, title: 'Second Post' }
];

# Your code here

Hint

Use const shouldRevalidate = true; to control revalidation.

3

Implement post submission with useFetcher

Use Remix's useFetcher hook to create a fetcher called postFetcher. Add a form that submits a new post title with postFetcher.submit. Use a handleSubmit function to call postFetcher.submit with the form data.

Remix

import { useFetcher } from '@remix-run/react';

const posts = [
  { id: 1, title: 'First Post' },
  { id: 2, title: 'Second Post' }
];

const shouldRevalidate = true;

// Your code here

Hint

Use useFetcher() to create postFetcher. Submit form data with postFetcher.submit.

4

Trigger revalidation after mutation

After submitting a new post, check if shouldRevalidate is true. If yes, call postFetcher.load(window.location.pathname) to revalidate the posts list.

Remix

import { useFetcher } from '@remix-run/react';

const posts = [
  { id: 1, title: 'First Post' },
  { id: 2, title: 'Second Post' }
];

const shouldRevalidate = true;

function PostForm() {
  const postFetcher = useFetcher();

  function handleSubmit(event) {
    event.preventDefault();
    const formData = new FormData(event.currentTarget);
    postFetcher.submit(formData, { method: 'post' });
    // Your code here
  }

  return (
    
      
      Add Post
    
  );
}

Hint

Use postFetcher.load(window.location.pathname) inside an if (shouldRevalidate) block.

Practice

1. What is the main purpose of revalidation after mutations in Remix Framework?

easy

A. To update the displayed data so the UI shows the latest changes

B. To prevent users from submitting forms

C. To delete data from the server automatically

D. To slow down the application for debugging

Solution

1. Step 1: Understand what mutation means

   Mutation means changing data, like adding or editing information.

2. Step 2: Understand revalidation's role

   Revalidation refreshes data after mutation so the UI shows the newest info.

3. Final Answer:

   To update the displayed data so the UI shows the latest changes -> Option A

4. Quick Check:

   Revalidation updates UI after data change = A [OK]

Hint: Revalidation means refreshing data after changes [OK]

Common Mistakes:

• Thinking revalidation deletes data
• Confusing revalidation with form blocking
• Believing revalidation slows the app

2. Which of the following is the correct way to trigger revalidation after a mutation in Remix?

easy

A. Call the function revalidate() from useRevalidator hook

B. Use window.location.reload() to refresh the page

C. Call fetch() without any parameters

D. Use setTimeout() to delay the mutation

Solution

1. Step 1: Identify the hook for revalidation

   Remix provides useRevalidator hook to manage revalidation.

2. Step 2: Use the revalidate() method from the hook

   Calling revalidate() triggers data refresh after mutation.

3. Final Answer:

   Call the function revalidate() from useRevalidator hook -> Option A

4. Quick Check:

   useRevalidator().revalidate() triggers update = C [OK]

Hint: Use revalidate() from useRevalidator to refresh data [OK]

Common Mistakes:

• Reloading the whole page instead of revalidating
• Calling fetch() without purpose
• Using setTimeout() unrelated to revalidation

3. Given this code snippet in a Remix component:

const revalidator = useRevalidator();
async function handleUpdate() {
  await fetch('/api/update', { method: 'POST' });
  revalidator.revalidate();
}
handleUpdate();

What happens after handleUpdate runs?

medium

A. Nothing happens because revalidate() is not called correctly

B. The page reloads completely

C. The UI data refreshes to show updated info from the server

D. The fetch request is canceled

Solution

1. Step 1: Analyze the fetch call

   The fetch sends a POST request to update data on the server.

2. Step 2: Understand revalidator.revalidate()

   Calling revalidate() refreshes the data shown in the UI after mutation.

3. Final Answer:

   The UI data refreshes to show updated info from the server -> Option C

4. Quick Check:

   fetch + revalidate() updates UI = B [OK]

Hint: After mutation, call revalidate() to refresh UI data [OK]

Common Mistakes:

• Assuming revalidate() reloads the whole page
• Thinking fetch cancels the request
• Believing revalidate() is not called

4. You wrote this code but the UI does not update after mutation:

const revalidator = useRevalidator();
async function saveData() {
  await fetch('/api/save', { method: 'POST' });
  revalidator();
}

What is the error?

medium

A. Missing await before revalidator

B. fetch needs a GET method instead of POST

C. saveData must be called inside useEffect

D. revalidator is a hook object, not a function; should call revalidator.revalidate()

Solution

1. Step 1: Check how revalidator is used

   revalidator is the object returned by useRevalidator hook, not a function itself.

2. Step 2: Correct method to call

   To trigger revalidation, call revalidator.revalidate(), not revalidator().

3. Final Answer:

   revalidator is a hook object, not a function; should call revalidator.revalidate() -> Option D

4. Quick Check:

   revalidator.revalidate(), not revalidator() = A [OK]

Hint: Call revalidator.revalidate(), not revalidator() [OK]

Common Mistakes:

• Calling revalidator() instead of revalidator.revalidate()
• Using wrong HTTP method for mutation
• Thinking revalidate must be awaited

5. You have a form that updates user info and calls an API mutation. You want the UI to show the updated user data immediately after submission without a full page reload. Which approach correctly uses Remix revalidation after mutation?

hard

A. Use setTimeout to delay UI update by 2 seconds

B. After the mutation fetch call, call revalidator.revalidate() from useRevalidator hook

C. Do nothing; Remix automatically updates UI after mutation

D. Reload the entire page using window.location.reload() after mutation

Solution

1. Step 1: Understand Remix's data update behavior

   Remix does not auto-refresh UI after mutations; manual revalidation is needed.

2. Step 2: Use useRevalidator hook to refresh data

   Calling revalidator.revalidate() after mutation triggers UI update without full reload.

3. Final Answer:

   After the mutation fetch call, call revalidator.revalidate() from useRevalidator hook -> Option B

4. Quick Check:

   Manual revalidate() call updates UI after mutation = D [OK]

Hint: Call revalidate() after mutation to update UI without reload [OK]

Common Mistakes:

• Relying on automatic UI update without revalidate()
• Reloading whole page instead of revalidating
• Using delays instead of proper revalidation