Unity-as-a-Library Sample Code

AppDelegate.swift

import UIKit
import UnityFramework

@main
class AppDelegate: UIResponder, UIApplicationDelegate {
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        func unityFramewokLoad() -> UnityFramework? {
            let bundlePath = "\(Bundle.main.bundlePath)/Frameworks/UnityFramework.framework"
            let bundle = Bundle(path: bundlePath)
            if let bundle = bundle, !bundle.isLoaded {
                bundle.load()
            }

            let ufw = bundle?.principalClass?.getInstance()
            if ufw?.appController() == nil {
                var header = _mh_execute_header
                ufw?.setExecuteHeader(&header)
            }
            return ufw
        }

        let ufw = unityFramewokLoad()
        ufw?.setDataBundleId("com.unity3d.framework")
        ufw?.runEmbedded(withArgc: CommandLine.argc, argv: CommandLine.unsafeArgv, appLaunchOpts: launchOptions)

        return true
    }
}

IOSPostProcessor.cs

#if UNITY_IOS
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor;
using UnityEditor.Build;
using UnityEditor.Build.Reporting;
using UnityEditor.Callbacks;
using UnityEditor.iOS.Xcode;

public class IOSPostProcessor : IPostprocessBuildWithReport
{
    public void OnPostprocessBuild(BuildReport report)
    {
        var summary = report.summary;
        var outputPath = summary.outputPath;
        var projectPath = outputPath + "/Unity-iPhone.xcodeproj/project.pbxproj";

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

        var guidTarget = pbx.GetUnityFrameworkTargetGuid();

        var guidHeader = pbx.FindFileGuidByProjectPath("Libraries/Plugins/iOS/UnityPlayerToIOS.h");
        pbx.AddPublicHeaderToBuild(guidTarget, guidHeader);

        var guidData = pbx.FindFileGuidByProjectPath("Data");
        var guidResPhase = pbx.GetResourcesBuildPhaseByTarget(guidTarget);
        pbx.AddFileToBuildSection(guidTarget, guidResPhase, guidData);
        
        pbx.SetBuildProperty(guidTarget, "BITCODE_GENERATION_MODE", "bitcode");

        pbx.WriteToFile(projectPath);
    }

    public int callbackOrder => 0;
}
#endif

NewBehaviourScript.cs

#if !UNITY_EDITOR && UNITY_IOS
using System.Runtime.InteropServices;
#endif
using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class NewBehaviourScript : MonoBehaviour
{
#if !UNITY_EDITOR && UNITY_IOS
    [DllImport("__Internal")]
    static extern void sendMessage(string msg);

    public void NativeMessage(string msg)
    {
        sendMessage(msg);
    }    
#else
    public void NativeMessage(string msg)
    {
        Debug.Log(msg);
    }
#endif
}

UnityPlayerToIOS.hh

#ifndef UnityPlayerToIOS_h
#define UnityPlayerToIOS_h

@protocol UnityCallback <NSObject>
@optional
@required
- (void)receiveMessage: (NSString *)msg;
@end

@interface UnityPlayerToIOS : NSObject
@property (class, nonatomic) id <UnityCallback> receiver;
+ (void)sendMessage: (NSString *)msg;
@end
#endif

UnityPlayerToIOS.mm

#import "UnityPlayerToIOS.h"

static id <UnityCallback> _receiver = nil;

@implementation UnityPlayerToIOS
+ (id <UnityCallback>) receiver {
    return _receiver;
}
+ (void)setReceiver: (id <UnityCallback>)receiver {
    _receiver = receiver;
}
+ (void)sendMessage: (NSString *)msg {
    if (_receiver) {
        [_receiver receiveMessage:msg];
    }
}
@end

extern "C" {
    void sendMessage(const char *msg) {
        [UnityPlayerToIOS sendMessage:[NSString stringWithCString: msg encoding:NSUTF8StringEncoding]];
    }
}

ViewController.swift

import UIKit
import UnityFramework
import RxSwift
import RxCocoa

class ViewController: UIViewController {
    let disposeBag = DisposeBag()
    
    @IBOutlet weak var unityParentView: UIView!
    @IBOutlet weak var button: UIButton!
       
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)

        guard let ufw = UnityFramework.getInstance() else { return }
        guard let unityView = ufw.appController()?.rootView else { return }
        guard let unityParentView = unityParentView else { return }

        unityParentView.addSubview(unityView)
        unityView.bounds = unityParentView.bounds
        
        ufw.setCallback(self)
        
        button.rx.tap
            .bind { [weak self] _ in
                // something
            }
            .disposed(by: disposeBag)
    }
}

extension ViewController : UnityCallback {
    func receiveMessage(_ msg: String!) {
        // something
    }
}