Integrating React-Native to an existing App - ios

Question

I'd like to integrate react-native modules in already existing iOS App but keeping both solutions separately.
Instead of doing this https://facebook.github.io/react-native/docs/integration-with-existing-apps.html which modifies the existing solution, I would like to have a standalone react-native solution and somehow import the Xcode project of the react-native app into my already existing app.
This allows me to continue developing the already existing app without being affected by the RN solution which installs and add libraries to the Xcode project.
Basically the concepto would be to export the react-native solution as a bundle or static library and import it in my already existing iOS App. After that interact with this library from the already existing iOS App and also allow the React-Native Solution library interact with the already existing app. There should be a way to communicate from the already existing app to the RN Solution library and also from the RN solution library with the already existing (i.e. for launching modules from the already existing iOS app and also from the RN solution be able to launch views of the already existing app)
Is this possible?

Answer 1

You can do most of the things you are referring. Excuse me if a miss something...
Runninig as standalone
If you don't have ios and android folders in your RN directory, you must run react-native eject from CLI.
React-native application can be started as a standalone native app using the CLI commands below:
react-native run-ios (only on MacOS)
react-native run-android
Add --port #### if the default is being used.
Both commands will start something like a sandbox native app which will load the JS inside. It will also start the Metro bundler which will serve the js bundle as well.
Loading RN into existing app
You need to add the native RN libraries for Android and iOS as dependencies, so you can use them to load either the JS bundle from the Dev server or insert the JS bundle within the native build.
To use the dev server run react-native start.
To build the JS as a file which will be added to the native package you must run:
react-native bundle ios
Followed by couple of options
--dev false or true
--entry-file index.ios.js change this to match your entry file. It may be just index.js. Be carefull to match the name inside Java/Obj-C code.
--bundle-output ../YOUR-EXISTING-IOS-APP/main.jsbundle
--assets-dest ../YOUR-EXISTING-IOS-APP
Communication
This happens over the RCTBridge.
Check this page for a explanation and examples how to access native functionality from the RN environment.