React Native Swift Module Singleton Pattern with Events Example

README.md

React Native Swift Module Singleton Pattern

If you are reading this tutorial please be aware that this is for advanced users that require a singleton pattern in their RN native module and some documentation detail is left out intentionally.

For the sake of this tutorial we will be using TestManager as our class.

Instructions

1. First of all you need to setup a swift class with a bridging header, in Xcode it will generate this for you upon creating a Swift file.
2. Create your swift class with the @objc directive.
3. Create a second class that has a static export of the class in singleton.
4. Follow the files below for a boilerplat example.

See files for more info

RNTestManager.m

#import "React/RCTBridgeModule.h"
#import "React/RCTEventEmitter.h"

@interface RCT_EXTERN_MODULE(RNTestManager, RCTEventEmitter)

RCT_EXTERN_METHOD(sendTest)

@end

RNTestManager.swift

@objc
class RNTestManager: RCTEventEmitter {
  private var manager: TestManager
  private var hasListeners = false
  
  override init() {
    super.init()
    manager = TestManager.shared
    manager.testEventCallback = testEventCallback
  }
  
  @objc
  func sendTest() {
    manager.sendTest()
  }
  
  func testEventCallback(_ message: String) {
    if hasListeners {
      sendEvent(withName: "testEvent", body: message)
    }
  }
  
  override func startObserving() {
    hasListeners = true
  }
  
  override func stopObserving() {
    hasListeners = false
  }
  
  override func supportedEvents() -> [String]! {
    return [
      "testEvent"
    ]
  }
  
  override class func requiresMainQueueSetup() -> Bool {
    return true
  }
}

TestManager.swift

class TestManager: NSObject {
  static let shared = TestManager()
  
  var testEventCallback: ((String) -> Void)?
  
  func sendTest() {
    testEventCallback?("This is a test")
  }
}