React Native async load bundled file

AppDelegate.m

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

#import "AppDelegate.h"

#import "RCTRootView.h"

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
  NSURL *jsCodeLocation;

  NSArray   *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
  NSString  *documentsDirectory = [paths objectAtIndex:0];
  NSString  *filePath = [NSString stringWithFormat:@"%@/%@", documentsDirectory,@"index.ios.bundle"];

  /**
   * Loading JavaScript code - uncomment the one you want.
   *
   * OPTION 1
   * Load from development server. Start the server from the repository root:
   *
   * $ npm start
   *
   * To run on device, change `localhost` to the IP address of your computer
   * (you can get this by typing `ifconfig` into the terminal and selecting the
   * `inet` value under `en0:`) and make sure your computer and iOS device are
   * on the same Wi-Fi network.
   */

   //jsCodeLocation = [NSURL URLWithString:@"http://localhost:8081/Examples/Movies/MoviesApp.ios.bundle?platform=ios&dev=true"];

  /**
   * OPTION 2
   * Load from pre-bundled file on disk. To re-generate the static bundle
   * from the root of your project directory, run
   *
   * $ react-native bundle --minify
   *
   * see http://facebook.github.io/react-native/docs/runningondevice.html
   */

  dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    NSURL  *url = [NSURL URLWithString:@"http://localhost:8081/index.ios.bundle?platform=ios&dev=true"];
    NSData *urlData = [NSData dataWithContentsOfURL:url];
    if ( urlData )
    {
      //saving is done on main thread
      dispatch_async(dispatch_get_main_queue(), ^{
        [urlData writeToFile:filePath atomically:YES];
      });
    }
  });

  BOOL fileExists = [[NSFileManager defaultManager] fileExistsAtPath:filePath];
  if (fileExists) {
    jsCodeLocation = [[NSURL alloc] initFileURLWithPath:filePath];
  } else {
    jsCodeLocation = [[NSBundle mainBundle] URLForResource:@"main" withExtension:@"jsbundle"];
  }

  RCTRootView *rootView = [[RCTRootView alloc] initWithBundleURL:jsCodeLocation
                                                      moduleName:@"AwesomeProject"
                                               initialProperties:nil
                                                   launchOptions:launchOptions];

  self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
  UIViewController *rootViewController = [[UIViewController alloc] init];
  rootViewController.view = rootView;
  self.window.rootViewController = rootViewController;
  [self.window makeKeyAndVisible];
  return YES;
}

@end