this project shows the needed steps to migrate the inital react-native setup to pure Swift without the usage of expo.

When creating a react-native project, it will create an Objective-C application delegate. After just replacing the Objective-C version with the Swift version, the run command will result in a error "No bundle URL present". This may have 2 reasons:

1. the code for getting the URL changed through the years - solved by providing this repository with the swift file
2. mismatch between running the cli command and the build setting. The react-native template doesn't set the DEBUG flag correctly. - solved by providing the setup steps here

xcode version: see XCODE_VERSION.md
react native verison: see package.json

• npx @react-native-community/cli@latest init SwiftReactNative
• open XCode
• open ios/SwiftReactNative.xcworkspace
• remove main.m, AppDelegate.h and AppDelegate.mm
• select File / New / File...
• select Swift File
• select folder ios/SwiftReactNative and name AppDelegate
• check "create bridge file" (or how it was spelled)
• add to SwiftReactNative-Bridge-Header.h

   #import <React/RCTBridgeModule.h>
   #import <React/RCTBridge.h>
   #import <React/RCTEventDispatcher.h>
   #import <React/RCTRootView.h>
   #import <React/RCTUtils.h>
   #import <React/RCTConvert.h>

• add to AppDelegate.swift

   import UIKit
   import React
   import Foundation
  
   @UIApplicationMain
   class AppDelegate: UIResponder, UIApplicationDelegate {
      var window: UIWindow?
      
      func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey : Any]? = nil) -> Bool {
         
         // MARK: ReactNative
         let bridge = RCTBridge(delegate: self, launchOptions: launchOptions)!
         let rootView = RCTRootView(bridge: bridge, moduleName: "SwiftReactNative", initialProperties: nil)
         
         self.window = UIWindow(frame: UIScreen.main.bounds)
         let rootViewController = UIViewController()
         
         rootViewController.view = rootView
         
         self.window!.rootViewController = rootViewController;
         self.window!.makeKeyAndVisible()
         
         return true
      }
   }
  
   // MARK: RCTBridgeDelegate
   extension AppDelegate: RCTBridgeDelegate {
      func sourceURL(for bridge: RCTBridge) -> URL? {
         // DEBUG requires SWIFT_ACTIVE_COMPILATION_CONDITIONS to contain DEBUG in a line in your target/build settings
         #if DEBUG
         NSLog("use metro server url - change schema build configuration to switch to release mode")
         return RCTBundleURLProvider.sharedSettings().jsBundleURL(forBundleRoot: "index")
         #else
         return Bundle.main.url(forResource: "main", withExtension: "jsbundle")
         #endif
      }
   }

• select project SwiftReactNative in left File navigator
• select target SwiftReactNative
• select tab Build Settings
• search for SWIFT_ACTIVE_COMPILATION_CONDITIONS
• extend the selection and add DEBUG on the right for Debug on the left