ifdef in Swift

AppDelegate.swift

//
//  AppDelegate.swift
//  ReactNativeSwift
//
//  Created by Gabriel Lai on 26/8/18.
//  Copyright © 2018 Facebook. All rights reserved.
//

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
  var window: UIWindow?
  
  func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey : Any]? = nil) -> Bool {
    
    let jsCodeLocation: URL
    
    #if DEBUG
      jsCodeLocation = RCTBundleURLProvider.sharedSettings().jsBundleURL(forBundleRoot: "index", fallbackResource: nil)
    #else
      jsCodeLocation = CodePush.bundleURL()
    #endif
    
    let rootView = RCTRootView(bundleURL: jsCodeLocation, moduleName: "ReactNativeSwift", initialProperties: nil, launchOptions: launchOptions)
    
    rootView?.backgroundColor = UIColor(red: 1.0, green: 1.0, blue: 1.0, alpha: 1)
    
    window = UIWindow(frame: UIScreen.main.bounds)
    let rootViewController = UIViewController()
    rootViewController.view = rootView
    window?.rootViewController = rootViewController
    window?.makeKeyAndVisible()
    
    return true
    
  }
  
}