UnitySwift

A simple Unity plug-in for iOS designed to serve as a starting point for creating new plugins that bridge Unity and Swift.

Getting Started

Follow the instructions below to set up the plugin and integrate it into your Unity project.

Prerequisites

• Unity 2019.x or later
• Xcode 11 or later

Integration into Your Own Project

1. Clone or download this repository.
2. Open the Unity project where you want to integrate the Swift plugin.
3. Copy the entire Assets/Plugins/iOS folder from this repository into your Unity project's Assets/Plugins folder.

Create a Unity plug-in from scratch

How to call Swift methods from Unity

Step 1: Create your Swift classes

Add the following code into Assets/Plugins/iOS/SwiftToUnity/Source/SwiftToUnity.swift:

import Foundation

@objc public class SwiftToUnity: NSObject {
    @objc public static let shared = SwiftToUnity()

    /// Returns the "Hello, Swift!" string.
    ///
    /// - Returns: The "Hello, Swift!" string.
    @objc public func swiftHelloWorld() -> String {
        return "Hello, Swift!"
    }
}

Note that here @obc instructs Swift to make classes or methods available to Objective-C as well as Swift code.

Step 2: Create a .mm bridge file

Add the following code into Assets/Plugins/iOS/SwiftToUnity/Source/SwiftToUnityBridge.mm:

#import <UnityFramework/UnityFramework-Swift.h>
#import "UnityInterface.h"

extern "C"
{
    char* cStringCopy(const char* string) {
        if (string == NULL) {
            return NULL;
        }

        size_t length = strlen(string) + 1;
        char* res = (char*) malloc(length);

        if (res != NULL) {
            memcpy(res, string, length);
        }

        return res;
    }

    char* cHelloWorld()
    {
        NSString *returnString = [[SwiftToUnity shared] swiftHelloWorld];
        return cStringCopy([returnString UTF8String]);
    }
}

The SwiftToUnityBridge.mm file is the bridging medium between Swift and Unity.

Step 3: Add UnityFramework.modulemap

Add the following code into Assets/Plugins/iOS/SwiftToUnity/Source/UnityFramework.modulemap:

framework module UnityFramework {
  umbrella header "UnityFramework.h"

  export *
  module * { export * }

  module UnityInterface {
      header "UnityInterface.h"

      export *
  }
}

Step 4: Add SwiftToUnityPostProcess.cs script

First, you will need to add the PostProcessing package to your Unity project.

To install the package, go to Window > Package Manager and switch the view from In Project to All. Select Post Processing in the list. In the right panel you'll find information about the package and a button to install or update to the latest available version for the version of Unity you are running.

Now add the following code into Assets/Plugins/iOS/SwiftToUnity/Editor/SwiftToUnityPostProcess.cs:

#if UNITY_IOS
using System.IO;
using UnityEngine;
using UnityEditor;
using UnityEditor.Callbacks;
using UnityEditor.iOS.Xcode;

public static class SwiftToUnityPostProcess
{
    [PostProcessBuild]
    public static void OnPostProcessBuild(BuildTarget buildTarget, string buildPath)
    {
        Debug.Log("OnPostProcessBuild: " + buildTarget);

        if (buildTarget == BuildTarget.iOS)
        {
            var projectPath = buildPath + "/Unity-iPhone.xcodeproj/project.pbxproj";

            var project = new PBXProject();
            project.ReadFromFile(projectPath);

            var unityFrameworkGuid = project.GetUnityFrameworkTargetGuid();

            // Modulemap
            project.AddBuildProperty(unityFrameworkGuid, "DEFINES_MODULE", "YES");

            var moduleFile = buildPath + "/UnityFramework/UnityFramework.modulemap";
            if (!File.Exists(moduleFile))
            {
                FileUtil.CopyFileOrDirectory("Assets/Plugins/iOS/SwiftToUnity/Source/UnityFramework.modulemap", moduleFile);
                project.AddFile(moduleFile, "UnityFramework/UnityFramework.modulemap");
                project.AddBuildProperty(unityFrameworkGuid, "MODULEMAP_FILE", "$(SRCROOT)/UnityFramework/UnityFramework.modulemap");
            }

            // Headers
            string unityInterfaceGuid = project.FindFileGuidByProjectPath("Classes/Unity/UnityInterface.h");
            project.AddPublicHeaderToBuild(unityFrameworkGuid, unityInterfaceGuid);

            string unityForwardDeclsGuid = project.FindFileGuidByProjectPath("Classes/Unity/UnityForwardDecls.h");
            project.AddPublicHeaderToBuild(unityFrameworkGuid, unityForwardDeclsGuid);

            string unityRenderingGuid = project.FindFileGuidByProjectPath("Classes/Unity/UnityRendering.h");
            project.AddPublicHeaderToBuild(unityFrameworkGuid, unityRenderingGuid);

            string unitySharedDeclsGuid = project.FindFileGuidByProjectPath("Classes/Unity/UnitySharedDecls.h");
            project.AddPublicHeaderToBuild(unityFrameworkGuid, unitySharedDeclsGuid);

            // Save project
            project.WriteToFile(projectPath);
        }

        Debug.Log("OnPostProcessBuild: Complete");
    }
}
#endif

Be sure to change the following line in SwiftPostProcess.cs script with the correct path to your UnityFramework.modulemap file:

FileUtil.CopyFileOrDirectory("Assets/Plugins/iOS/SwiftToUnity/Source/UnityFramework.modulemap", moduleFile);

Step 5: Call your Swift methods from Unity

using System.Runtime.InteropServices;
using UnityEngine;

public class CanvasScript : MonoBehaviour
{
    [DllImport("__Internal")]
    private static extern string cHelloWorld();

    private void Start()
    {
        cHelloWorld();
    }
}

How to call Unity methods from Swift

To call Unity methods from Swift, use UnitySendMessage function like below:

// SwiftToUnity.swift
import Foundation

@objc public class SwiftToUnity: NSObject {
    @objc public static let shared = SwiftToUnity()

    /// Sends a "Hello World" message to the "Canvas" GameObject by calling the "OnMessageReceived" script method on that object with the "Hello World!" message.
    @objc public func swiftSendHelloWorldMessage() {
        // The UnitySendMessage function has three parameters: the name of the target GameObject, the script method to call on that object and the message string to pass to the called method.
        UnitySendMessage("Canvas", "OnMessageReceived", "Hello World!");
    }
}

See SwiftToUnity.swift.

For more information about UnitySendMessage, check out Unity's Documentation.

License

This project is licensed under the MIT License.