Step by Step with frb

1.Initialize Rust

Run this when starting a new project only. Otherwise, skip to step 2.

Create src_rust folder & run cargo init command.

2. Install Cargo Tools

cargo install cargo-xcode cargo-lipo

3. Install target for different platforms

# Android
rustup target add \
    aarch64-linux-android \
    armv7-linux-androideabi \
    x86_64-linux-android \
    i686-linux-android

# iOS
rustup target add \
    aarch64-apple-ios \
    x86_64-apple-ios \
    aarch64-apple-ios-sim

4. Update Cargo.toml to use frb

Add crate-type(staticlib for ios and cdylib for other platform) under lib and flutter_rust_bridge under dependencies in Cargo.toml.

Run these commands.

flutter pub add ffi flutter_rust_bridge
flutter pub add ffigen --dev
flutter pub global activate ffigen

# and then install llvm.

Install flutter_rust_bridge_codegen binary:

# install the flutter_rust_bridge_codegen binary
# in ~/.cargo/bin/flutter_rust_bridge_codegen
cargo install flutter_rust_bridge_codegen

Copy this code in main.dart to load the rust builds:

import 'dart:ffi';
import 'dart:io';

import 'package:flutter/material.dart';

import 'bridge_generated.dart';

const base = 'step'; // the name is related with cargo.toml [lib] name.
final path = Platform.isWindows ? '$base.dll' : 'lib$base.so';
late final dylib = Platform.isIOS
    ? DynamicLibrary.process()
    : Platform.isMacOS
        ? DynamicLibrary.executable()
        : DynamicLibrary.open(path);
late final api = SrcRustImpl(dylib);

5. Setup iOS

1. Generates bindings code between Rust and Flutter, also utilities for Xcode.

   flutter_rust_bridge_codegen -r src_rust/src/api.rs -d lib/bridge_generated.dart -c ios/Runner/bridge_generated.h

2. Add lib target in Cargo.toml likes below

    [lib]
    name = "step"
    crate-type = ["staticlib", "lib"]

3. Builds Rust code into step.a and copies the step.a into Runner directory so that Xcode can search for the lib while linking

   cd src_rust \
   cargo lipo && cp target/universal/debug/libstep.a ../ios/Runner 

4. Declares #import "bridge_generated.h" in Runner-Bridging-Header.h file & add dummy method in AppDelegate.swift file likes below:

   GeneratedPluginRegistrant.register(with: self)
   print("dummy_value=\(dummy_method_to_enforce_bundling())"); // add dummy method here
   return super.application(application, didFinishLaunchingWithOptions: launchOptions)

5. Open the ios folder in Xcode, in Targets > Runner > Build Phases tab, check the step.a was in Link Binary With Libraries (If there's error maybe we should ignore arm64 only in Targets > Runner > Build Settings)

6. Setup Android

Run command in src_rust folder

 cargo install cargo-ndk && cargo ndk -t x86 -t armeabi-v7a -t arm64-v8a -t x86_64 -o ../android/app/src/main/jniLibs build
 # make sure you sucessfully install NDK)

7. Setup macOS

1. Generates bindings code between Rust and Flutter, also utilities for Xcode.

   flutter_rust_bridge_codegen -r src_rust/src/api.rs -d lib/bridge_generated.dart -c macos/Runner/bridge_generated.h

2. There is no bridging header file to tell Xcode about our bridge generated code. We have to tell Xcode another way, in Targets > Runner > Build Settings tab, set the Objective-C Bridging Header to be Runner/bridge_generated.h. And add dummy method same as we did in ios setup part:

   // ...
   override func applicationShouldTerminateAfterLastWindowClosed(_ sender: NSApplication) -> Bool {
       print("dummy_value=\(dummy_method_to_enforce_bundling())"); // add dummy method here
       return false
   }
   // ...  

3. Run cargo xcode within Rust directory and it will generate *.xcodeproj folder inside Rust project directory. DO NOT open it util you add generated *.xcodeproj under macos Xcode project.

   

4. Linking the libs by opening Targets > Runner > Build Phases tab:

   • In Dependencies add dynamic lib step-cdylib(.cdylib file).

   • In Link Binary with Libraries add static lib step.a (.a file).

8. Setup Linux

1. Generates bindings code between Rust and Flutter.

   flutter_rust_bridge_codegen -r src_rust/src/api.rs -d lib/bridge_generated.dart

2. Add lib target in Cargo.toml likes below:

   [lib]
   name = "step"
   crate-type = ["lib", "staticlib", "cdylib"]

3. If the machine is not arm64 ,you can use corrosion approach docs or a workaround for arm64 is to ignore rust.cmake and manually configure CMake to build and bundle the Rust library.

• Go to linux/CMakeLists.txt and adding this to the bottom of CMakeLists.txt file.

  set(NATIVE_LIBRARY "${CMAKE_SOURCE_DIR}/../src_rust/target/aarch64-unknown-linux-gnu/release/libstep.so")
  install(FILES "${NATIVE_LIBRARY}" DESTINATION "${INSTALL_BUNDLE_LIB_DIR}"
  COMPONENT Runtime)

• Generate .so build from terminal.

  cargo build --target aarch64-unknown-linux-gnu --release

9. Setup Window

1. Generates bindings code between Rust and Flutter.

   flutter_rust_bridge_codegen -r src_rust/src/api.rs -d lib/bridge_generated.dart

2. Note that: There are two options. First option is installing corrosion directly & use it and Second option is installing corrosion into the machine system.

   • First Option

   1. Create rust.cmake inside windows folder and add this.

      
          include(FetchContent)
          FetchContent_Declare(
              Corrosion
              GIT_REPOSITORY https://github.com/AndrewGaspar/corrosion.git
              GIT_TAG origin/master # Optionally specify a version tag or branch here
          )
          FetchContent_MakeAvailable(Corrosion)
          corrosion_import_crate(MANIFEST_PATH ../src_rust/Cargo.toml)
          # Flutter-specific
          set(CRATE_NAME "step")
          target_link_libraries(${BINARY_NAME} PRIVATE ${CRATE_NAME})
          list(APPEND PLUGIN_BUNDLED_LIBRARIES $<TARGET_FILE:${CRATE_NAME}-shared>)
      
      

   2. include rust.cmake inside CMakeLists.txt.

      
       include(./rust.cmake)
      
      

   • Second Option

   1. Install Corrosion.

       # make sure cmake is installed.
       git clone https://github.com/corrosion-rs/corrosion.git
      
       cmake -Scorrosion -Bbuild -DCMAKE_BUILD_TYPE=Release
      
       cmake --build build --config Release
      
       cmake --install build --config Release
      

   2. Create mrrust.cmake inside windows folder add this.

      
          find_package(Corrosion REQUIRED)
          corrosion_import_crate(MANIFEST_PATH ../src_rust/Cargo.toml)
      
          # Flutter-specific
      
          set(CRATE_NAME "step")
          target_link_libraries(${BINARY_NAME} PRIVATE ${CRATE_NAME})
          list(APPEND PLUGIN_BUNDLED_LIBRARIES $<TARGET_FILE:${CRATE_NAME}-shared>)
      

   3. include mrrust.cmake inside CMakeLists.txt.

      
       include(./mrrust.cmake)