How my react js code can interact with existing Obj-C logic? - react-native

Question

I have existing Obj-C project with rich business logic. I wanna try using React Native on the particular screen (I mean View Controller in terms of Cocoa), but every example I see in repo contains logic in javascript. How can I treat React Native as rendering, but pass user actions to my Objective-C code?
EDIT 31 march 2015:
Native view module does not seem to be a good solution, because native modules get instanciated from React code. Thus if I want to use already created view model for that view controller, I need to have some singleton, which will be like a some shared state on the side. I think this is bad.

Answer 1

It's not possible for React views to call native methods directly without going through JavaScript, unless you create custom native view plugins for literally everything onscreen.
Your best bet is probably to create a custom native module that exports all the native methods you want to call, then write a minimal React JavaScript application that does nothing except forward touch events from the views to your module by calling those methods.
If you need to communicate back to the JS application, your module can either use callbacks passed to your exported methods, or broadcast events which the JS code can observe.
To get the most out of React Native though, I'd recommend that you try to keep all the view and controller logic in the JS part, and only expose the business logic from the native side. Otherwise you lose all the benefits of rapid reloading to test changes, etc.

Answer 2

I have the same problem and what I did to solve it:
Create Native Module wrapper around NSNotificationCenter, so javascript code could publish iOS events.
Subscribe for that event within ReactController-wrapper around React-Native code.
Raise event when user clicked button (when we need to give control back to objective-c) with needed data to pass as dictionary.
Catch event from ReactController-wrapper (objective-c), process data, open other controllers/etc.
Using React Native within existing iOS app for some views only

Answer 3

Have a look at the documentation:
http://facebook.github.io/react-native/docs/nativemodulesios.html#content
React Native provides "Native Modules" as a way of bridging between Obj-C and JavaScript. There's also a little bit more about this on the React Native homepage:
http://facebook.github.io/react-native/
Under the "Extensibility" heading, it shows how to expose custom iOS views.

Answer 4

IF you implement RCTRootView in your view controller you can use it to access RTCBridge and then from this gain access to your module.
This will allow you to keep a reference of your view controller inside your module, making you able to pass calls to method directly instead of relying on NSNotifications.
example :
In your view controller
let reactView = RCTRootView(bundleURL: jsCodeLocation, moduleName: "MyReactApp", initialProperties: nil, launchOptions: nil)
self.reactBridge = reactView.bridge
let myModule = self.reactBridge.module(for: MYModuleClass.self) as! MYModuleClass
myModule.viewController = self
And in your module keep the reference :
#objc(MYModuleClass)
class MYModuleClass: NSObject {
weak var viewController: MyViewController!
}