UPDATE: The API for this changed slightly on 9th April. Rather than using just RCT_EXPORT you must use RCT_EXPORT_MODULE for the class and RCT_EXPORT_METHOD on the methods you want to export. The article has been amended to reflect this.
For whatever reason, you want to send a string from the Obj-C side down to React Native. One example might be to do something with the device’s file system, like retrieve the path of a resource or document. In Xcode, use File > New > File… to create a new Cocoa Touch class that extends NSObject. I’ve called the class SomeString:
If you’ve got the Chrome Debugger open (press CMD+D in the Simulator to pop it open) then you’ll see your string logged in the console. Easy peasy!