[rust] ios build with cbindgen

rust-ios-build-with-cbindgen.md

Here’s a minimal, App Store–ready Rust → iOS dynamic framework setup, including the folder structure, header generation, shell build script, and framework layout. This is exactly how an industry team would structure a small Rust library for iOS.

---

1. Folder Structure

my_rust_lib/
├── Cargo.toml
├── cbindgen.toml
├── include/
│   └── my_rust_lib.h          # generated automatically by cbindgen
├── src/
│   ├── lib.rs                 # entry point
│   ├── core/                  # cross-platform logic
│   │   ├── mod.rs
│   │   ├── crypto.rs
│   │   └── utils.rs
│   └── ios/
│       └── ffi.rs             # #[no_mangle] extern "C" functions
└── ios_build/
    ├── build.sh               # shell script to build framework
    └── Info.plist             # minimal plist for framework

---

2. ffi.rs Example

// src/ios/ffi.rs
#[cfg(target_os = "ios")]
#[no_mangle]
pub extern "C" fn encrypt_ios(data: *const u8, len: usize, out_len: *mut usize) -> *mut u8 {
    let slice = unsafe { std::slice::from_raw_parts(data, len) };
    let encrypted = crate::core::encrypt(slice);
    let ptr = encrypted.as_ptr();
    *out_len = encrypted.len();
    std::mem::forget(encrypted); // transfer ownership to caller
    ptr as *mut u8
}

---

3. cbindgen.toml Example

language = "C"
include_version = false
autogen_tag = "Automatically generated, do not edit."
output = "include/my_rust_lib.h"

---

4. Minimal Info.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN"
 "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>CFBundleIdentifier</key>
    <string>org.example.MyRustLib</string>
    <key>CFBundleName</key>
    <string>MyRustLib</string>
    <key>CFBundleVersion</key>
    <string>1.0</string>
</dict>
</plist>

---

5. Minimal Shell Script: ios_build/build.sh

#!/usr/bin/env bash
set -e

# 1. Generate C header
cbindgen --config ../cbindgen.toml --crate my_rust_lib --output ../include/my_rust_lib.h
echo "Header generated at include/my_rust_lib.h"

# 2. Build Rust dynamic library for iOS device
cargo build --release --target aarch64-apple-ios

# 3. Prepare framework
rm -rf MyRustLib.framework
mkdir -p MyRustLib.framework/Headers

# 4. Copy Rust library and rename (remove .dylib)
cp target/aarch64-apple-ios/release/libmy_rust_lib.dylib MyRustLib.framework/MyRustLib

# 5. Copy header and Info.plist
cp ../include/my_rust_lib.h MyRustLib.framework/Headers/
cp Info.plist MyRustLib.framework/

echo "Framework ready: MyRustLib.framework"

---

6. Resulting Framework Layout

MyRustLib.framework/
├── MyRustLib                # Rust dynamic library (no extension)
├── Headers/
│   └── my_rust_lib.h        # generated header
└── Info.plist               # required for framework

• Xcode can now import the framework, call the Rust functions via the header, and App Store submission is allowed.
• Only the device architecture (ios-arm64) is included; simulator support can be added later if needed.

---

This setup is minimal, clean, and App Store–ready. It also keeps the core Rust logic isolated and header generation fully automated via shell script.

If you want, I can also show a complete lib.rs + core module minimal example so you could drop this into a new project and build the XCFramework immediately. Do you want me to do that?