Building a nim library to be consumed from a go library from mobile or desktop environments

Requirements

• go
• gomobile
• nodejs
• yarn
• AndroidSDK
• AndroidNDK
• Build essentials (gcc/clang)

Clone the repo

git clone https://github.com/richard-ramos/gonimffi.git
cd gonimffi
git submodule init

Android

Nim

1. Edit in nim/nim.cfg the clang.path variables to point to the folder in which the AndroidNDK clang resides
2. Edit in nim/Makefile the variable ANDROID_SYSROOT to point to the sysroot folder of AndroidNDK
3. Execute

cd nim
make build-mobile-android

This will generate libhello.so libraries for the four architectures supported in Android. It will proceed to copy these files in mobile/AwesomeProject/android/app/src/main/jniLibs

To add more functions, edit nim/hello.nim, and nim/libhello.h. The function NimMain() must be called in an initialization function somewhere in order to initialize Nim's garbage collector.

You might need to link against Android libraries depending on the functions you use. i.e., if you use echo, then you need to link against liblog, which is done with --passL:-llog (already done on the Makefile)

Go

1. Execute

cd go
make build-mobile-android

This will use gomobile to generate the file hello.aar. This will be copied in mobile/AwesomeProject/android/app/libs/.

To add any additional function, edit go/mobile/hello.go. gomobile will export functions that start with an Uppercase. Not all datatypes are supported: bool, string, int, uint, int8, uint8, int16, uint16, int32, uint32, int64, uint64, uintptr, byte, rune, float32, float64, complex64, complex128.

React Native

1. Install dependencies

cd mobile/AwesomeProject
yarn

To load the nim and go libraries, mobile/AwesomeProject/android/app/build.gradle was edited with:

android {
    ...
    sourceSets {
        main {
            jniLibs {
                srcDirs 'src/main/jniLibs'
            }
        }
    }
    ...
}

dependencies {
    ...
    implementation fileTree(dir: "libs", include: ["*.aar"])
    ... 
}

The following files were created:

• mobile/AwesomeProject/android/app/src/main/java/com/awesomeproject/ReactNativeModule.kt
• mobile/AwesomeProject/android/app/src/main/java/com/awesomeproject/ReactNativePackage.kt

Additional functions must be added to ReactNativeModule.kt.

In mobile/AwesomeProject/android/app/src/main/java/com/awesomeproject/MainActivity.kt libhello.so (the nim library) is loaded. This is necessary so the go library (hello.aar) is able to work (otherwise you'll get an Undefined Reference error)

    companion object {
        init {
            System.loadLibrary("hello")
        }
    }

Finally, an invocation to the function we exposed in Go, can be found in mobile/AwesomeProject/App.tsx. This should print a hello world in the android logs.

Testing

Using the emulator, assuming you have a Pixel6 API 33 image (this assumes the platform-tools folder from the AndroidNDK is available on the PATH)

./emulator -avd Pixel_6_API_33

Docs on how to create an image can be found in https://developer.android.com/studio/run/managing-avds

Once the emulator is running, in a different terminal:

cd mobile/AwesomeProject
npm run start

And press a key once a menu appears to run the app on Android.

If using a mobile device, refer to this documentation: https://reactnative.dev/docs/running-on-device

To see the hello world message, you need to use adb logcat (available on the AndroidNDK platform-tools folder)

IOS

TODO

Desktop (Linux)

This assumes you're building in a AMD64 machine with linux

Nim

cd nim
make build-desktop-linux

This will generate a shared library libhello.so and copy it into the desktop folder.

Go

cd go
make build-desktop-linux

This will generate a shared library libgohello.so and copy it into the desktop folder.

Desktop app

For the purposes of this example, we use a simple C program:

cd desktop
make
make run

Desktop (MacOSX)

TODO

Desktop (Windows)

TODO