feat(RCTAppDelegate): Implement RCTRootViewFactory

[okwasniewski]

Summary:

This PR implements RCTRootViewFactory a utility class (suggested by @cipolleschi) that returns proper RCTRootView based on the current environment state (new arch/old arch/bridgeless). This class aims to preserve background compatibility by implementing a configuration class forwarding necessary class to RCTAppDelegate.

Brownfield use case

This PR leverages the RCTRootViewFactory in RCTAppDelegate for the default initialization of React Native (greenfield).

Here is an example of creating a Brownfield integration (without RCTAppDelegate) using this class (can be later added to docs):

1. Store reference to rootViewFactory and to UIWindow

AppDelegate.h:

@interface AppDelegate : UIResponder <UIApplicationDelegate>

@property(nonatomic, strong) UIWindow* window;
@property(nonatomic, strong) RCTRootViewFactory* rootViewFactory;

@end

2. Create an initial configuration using RCTRootViewFactoryConfiguration and initialize RCTRootViewFactory using it. Then you can use the factory to create a new RCTRootView without worrying about old arch/new arch/bridgeless.

AppDelegate.mm

@implementation AppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary<UIApplicationLaunchOptionsKey,id> *)launchOptions {
  
  // Create configuration
 RCTRootViewFactoryConfiguration *configuration = [[RCTRootViewFactoryConfiguration alloc] initWithBundleURL:self.bundleURL 
                                                                                                 newArchEnabled:self.fabricEnabled
                                                                                             turboModuleEnabled:self.turboModuleEnabled
                                                                                              bridgelessEnabled:self.bridgelessEnabled];

  
  // Initialize RCTRootViewFactory
  self.rootViewFactory = [[RCTRootViewFactory alloc] initWithConfiguration:configuration];
  
  // Create main root view
  UIView *rootView = [self.rootViewFactory viewWithModuleName:@"RNTesterApp" initialProperties:@{} launchOptions:launchOptions];
  
  // Set main window as you prefer for your Brownfield integration.
  self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
  UIViewController *rootViewController = [UIViewController new];
  rootViewController.view = rootView;
  self.window.rootViewController = rootViewController;
  [self.window makeKeyAndVisible];
  
  // Later in the codebase you can initialize more rootView's using rootViewFactory.
  
  return YES;
}
@end

Changelog:

[INTERNAL] [ADDED] - Implement RCTRootViewFactory

Test Plan:

Check if root view is properly created on app initialization

[cipolleschi]

I don't think that this is what you actually want.

Here, you are not just creating another view.
You are also creating a new Bridge/ReactHost for every different window. You are initializing the Turbomodule system multple times, and so on.

Also, we are overloading the RCTAppDelegate with responsibilities that it should not have.

The App delegate responsibilityi is to inizialize the app and act as a bridge between the OS and the app. If we want other capabilities, we should have different classes.

For example, we should create an RCTViewFactory or a RCRootViewFactory that is able to provide the root view based on the current state of Bridge/React Host, other parameters.

[okwasniewski]

@cipolleschi Creating RCTRootViewFactory would be the ideal solution but I didn't want to introduce too many changes. However I'm not re-creating key components every time with this approach: self.bridge, _reactHost and bridgeAdapter are created only once on the first call (I accidentally pushed code without this change at first).

Also, I can work on implementing the RCTRootViewFactory (if you are okay with having this)

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	17,750,514	+16
android	hermes	armeabi-v7a	n/a	--
android	hermes	x86	n/a	--
android	hermes	x86_64	n/a	--
android	jsc	arm64-v8a	21,108,987	-1
android	jsc	armeabi-v7a	n/a	--
android	jsc	x86	n/a	--
android	jsc	x86_64	n/a	--

Base commit: 496724f
Branch: main

[okwasniewski]

@cipolleschi I decided to jump straight into it and implement this class, I think it will make initialization of RN a lot easier also in brownfield apps.

I tried to implement everything in a backward-compatible way

[okwasniewski]

Hi, @cipolleschi would you be willing to take a look at this and let me know if you're interested in pursuing it? It may require some polish, but I'd like to know if you're open to moving forward with this idea or if I should explore alternative options for react-native-visionos.

[cipolleschi]

Hi @okwasniewski thanks for the proposal.
I'm not completely convinced about it.
First of all, we are breaking the AppDelegate interface. I understand that practically nothing changes because we are moving all the methods to a protocol which is implemented by the AppDelegate, but I'd rather not doing this.
It will make harder to reach out for the documentation.

Secondly, I don't think that everything is properly supported. I saw that you are hardcoding fabricEnabled to true and bridgelessEnabled to false, for example.

[okwasniewski]

Thanks for your review @cipolleschi I think now it's much better the public interface is not changed except for the runtimeSchedulerEnabled, bridge and bridgeAdapter but those are properties that users shouldn't override.

I also fixed those hardcoded values

[okwasniewski]

@cipolleschi As discussed offline, I've refactored the implementation to drop the delegate pattern and now we pass a configuration object. I've also validated that this PR fixes a bug with RCTRootViewExample when running bridgeless mode. RCTRootViewFactory is now decoupled from the RCTAppDelegate (so that we can move it). I've also added a short documentation to the PR description on brownfield integration using this class (tested it out on RNTester without RCTAppDelegate). Let me know what you think 👍🏻

[cipolleschi]

Just a small nit, but it looks good to me. Thank you so much for this improvement! :D

[facebook-github-bot]

@cipolleschi has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

[okwasniewski]

Hey @cipolleschi, I've rebased the PR on top of the latest changes, is there anything I can do to help you get this merged?

[cipolleschi]

Hi @okwasniewski, sorry for the delay. I was quite busy in the past couple of weeks dealing with other high priority tasks and I couldn't really spend some time on this.

I'll try to make this move forward this week. Thank you for your patience!

[facebook-github-bot]

@cipolleschi merged this pull request in ec928d7.