expo-swift-example

Example of writing Swift modules in Expo

How To

First detach your expo project with:

exp detach

Then open your iOS project, and add a swift file. You will also need a .m file of the same name.

• DemoModule.swift
• DemoModule.m

You should have been prompted to add a bridging header. To check to make sure your header is linked:

• Click on the project Icon (Blue icon on the top left)
• Click the Build Settings tab
• Go to the section Swift Compiler - General
  • The value for Objective-C Bridging Header should be [project]/[project]-Bridging-Header.h.
  • Ex: expo-swift-example/expo-swift-example-Bridging-Header.h

In your bridging header, import React Native libraries:

#import <React/RCTBridgeModule.h>
#import <React/RCTEventEmitter.h>

Now in your swift file:

@objc(DemoModule)
class DemoModule: RCTEventEmitter {
    @objc func someMethod(_ input: String) -> Void {}
    override func supportedEvents() -> [String]! {
      return []
    }
    @objc override func constantsToExport() -> [AnyHashable : Any]! {
      return []
    }
}

In your .m file:

#import <React/RCTBridgeModule.h>
#import <React/RCTEventEmitter.h>
@interface RCT_EXTERN_MODULE(DemoModule, NSObject)
RCT_EXTERN_METHOD(someMethod:(NSString *)input);
@end

And in JS:

import { NativeModules } from 'react-native';
NativeModules.DemoModule.someMethod(input);