Can I expose a Swift function to React Native without using Objective-C (pure swift)?

Question

I wonder if I can expose my func navigateToLoginWidget to React Native. So that it can be triggered from RN.

I have managed to change the Objective-C template that comes with React Native to Swift like so:

import Foundation
import IBMCloudAppID
import BMSCore

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
  
  var window: UIWindow?
  var bridge: RCTBridge!

  func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    
    // initializing App ID SDK
    let region = AppID.REGION_SOMEWHERE
    let backendGUID = "MY_TENANT_ID_FROM_IBM"
    AppID.sharedInstance.initialize(tenantId: backendGUID, region: region)
    
    // Initializing React Native front-end with Swift instead of Obj-c template
    let jsCodeLocation: URL

    jsCodeLocation = RCTBundleURLProvider.sharedSettings().jsBundleURL(forBundleRoot: "index.js", fallbackResource:nil)
    let rootView = RCTRootView(bundleURL: jsCodeLocation, moduleName: "MY_PROJECT_NAME", initialProperties: nil, launchOptions: launchOptions)
    let rootViewController = UIViewController()
    rootViewController.view = rootView

    self.window = UIWindow(frame: UIScreen.main.bounds)
    self.window?.rootViewController = rootViewController
    self.window?.makeKeyAndVisible()

    return true
  }
  
  func application(_ application: UIApplication, open url: URL, options :[UIApplication.OpenURLOptionsKey : Any]) -> Bool {
      return AppID.sharedInstance.application(application, open: url, options: options)
  }
  
  func navigateToLoginWidget(_ sender : Any) {
    print("clicked")
    AppID.sharedInstance.loginWidget?.launch(delegate: SigninDelegate)
  }
  
}

I would normally have this function in another module called SigninDelegate.swift, but I have included it in the same class for explanatory purposes.

Answer 1

According to the official documentation:

Swift doesn't have support for macros so exposing it to React Native requires a bit more setup but works relatively the same.

So yes, it is possible, but some setup is needed. Check the docs in the link above for the steps you need to follow to set it up.