How to Use Rust with React Native via FFI

You cannot directly use Rust with React Native via FFI because React Native's JavaScript engine (Hermes or JSC) cannot load native C libraries compiled by Rust. Instead, you must compile your Rust code into a native C++ library (.so/.dylib/.a) using the cc crate or bindgen, then link that library into your React Native project's native modules.

# 1. Create a Rust library with #[no_mangle] and extern "C" functions
cargo new --lib my_rust_module
cd my_rust_module

# 2. Add cc to Cargo.toml dependencies
# [dependencies]
# cc = "1.0"

# 3. Compile to a static library (example for Linux)
cargo build --release
# Then use the resulting .a file in your React Native C++ build (CMakeLists.txt or Android.mk)

Note: You must wrap your Rust logic in extern "C" functions and handle memory manually or via FFI-safe wrappers, as React Native's native modules expect C++ interfaces.

Rust code can't talk directly to React Native because they speak different languages. You have to turn your Rust code into a standard C++ library first, then connect that library to your React Native app. Think of it like translating a book into a language the reader understands before they can read it.