counter-middleware

Counter (Middleware) example

Builds on counter-http by adding a "I'm feeling lucky" button that adjusts the counter by a random amount between -5 and 5. The random number generation is handled by middleware — Rust code that intercepts effects before they reach the shell.

Architecture

The shared directory adds a custom Random capability on top of the HTTP counter. This demonstrates:

• Defining a custom Operation (request/response types) for the middleware
• Implementing EffectMiddleware to handle the operation in Rust
• Wiring middleware into the core with .handle_effects_using()
• Narrowing the Effect enum with .map_effect() so the shell never sees Random effects

Two cores

This example has two FFI bridges that wire up the core differently:

• Native (uniffi) — The RngMiddleware intercepts Random effects and handles them entirely in Rust. The shell never sees them.
• Web (wasm_bindgen) — Middleware can't run in wasm (it uses std::thread::spawn), so Random effects pass through to the shell, which handles them in JavaScript. This demonstrates the app working, but not the middleware feature itself.

Shells

• SwiftUI (iOS/macOS) — apple/
• Android/Kotlin — android/
• Leptos — web-leptos/
• NextJS — web-nextjs/

Running

1. Choose a shell you're interested in, i.e. apple or android.
2. In the shell's directory, run just doctor to make sure you have the right tools installed
3. Run just dev to generate code and build that shell
4. For apple and android shells, open the IDE. For others, run just serve in the shell directory.