Attempts at implementing background tasks in React Native iOS

BackgroundTask.h

//
//  BackgroundTask.h
//  tomtrack
//
//  Created by Liam Edwards-Playne on 13/02/2016.
//

#import "RCTBridgeModule.h"

@interface BackgroundTask : NSObject <RCTBridgeModule>

@end

BackgroundTask.m

//
//  BackgroundTask.m
//  tomtrack
//
//  Created by Liam Edwards-Playne on 13/02/2016.
//

#import <Foundation/Foundation.h>

#import "BackgroundTask.h"
#import "RCTUtils.h"


/*
 Sample: 
 
 BackgroundTask.beginBackgroundTask("gpsTracking", () => {})
 
 */

@implementation BackgroundTask


RCT_EXPORT_MODULE();

#pragma mark - Public API

RCT_EXPORT_METHOD(beginBackgroundTask:(NSString *)taskName jsCallback:(RCTResponseSenderBlock)jsCallback)
{
  UIApplication *application = RCTSharedApplication();
  
  __block UIBackgroundTaskIdentifier bgTask = [application beginBackgroundTaskWithName:taskName expirationHandler:^{
    // Clean up any unfinished task business by marking where you
    // stopped or ending the task outright.
    [application endBackgroundTask:bgTask];
    bgTask = UIBackgroundTaskInvalid;
  }];
  
  // Start the long-running task and return immediately.
  dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    printf("Running in the background\n");
    // Call the JS code
    jsCallback(@[]);
    printf("Back from the JS\n");
    
    [application endBackgroundTask:bgTask];
    bgTask = UIBackgroundTaskInvalid;
  });
}

@end

example.js

var BackgroundTask = require('react-native').NativeModules.BackgroundTask;
BackgroundTask.beginTask("taskName", function(){})