Chapter 19: File Uploads in Elixir

Multipart form data and file handling. In this chapter, you will learn file uploads in depth with Elixir code examples, explanations, and best practices.

Overview

This chapter covers file uploads for Kungfu.js developers using Elixir. We will start with the basics, move through practical examples, and end with advanced techniques and common pitfalls.

Why This Matters

Understanding file uploads is essential because it is a core part of building web applications. Every real-world app needs to handle multipart form data and file handling. Skipping this chapter would leave a gap in your knowledge that would cause problems later.

Code Example

Here is how to handle requests and responses in Elixir:

// Handle file upload (multipart/form-data)
app.post('/upload', (req) => {
    // req.body contains multipart form data
    // Parse it to extract files
    // The Rust core handles the multipart parsing
    return { status: 201, body: 'File uploaded' };
});

Common Mistakes

• Not reading the documentation: Always check the API reference when something does not work as expected.
• Skipping security: Never disable the default middleware unless you have a very good reason. Security is not optional.
• Not testing: Write tests for your handlers. Kungfu.js makes this easy with the built-in test utilities.

Summary

In this chapter, you learned about file uploads in Elixir. You saw code examples, understood how things work under the hood, and learned about common mistakes to avoid.

What is Next?

In chapter 20, we will cover Cookies and Sessions: Set cookies, manage sessions, SameSite.