Easy example of Grand Central Dispatch

Question

I\'m newbie programming for mac and i\'m really surprised on Grand Central Dispatch. I read about that and looks like the perfect solution for parallel programming. I worked wit

Answer 1

-(void)Search_load_Scraping{

    Reachability *reachability = [Reachability reachabilityForInternetConnection];
    NetworkStatus internetStatus = [reachability currentReachabilityStatus];
    if (internetStatus != NotReachable)
    {



    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0),
                   ^{

                       TrainInfo  *TrnObj=[[TrainInfo alloc]init];
                       ScrapingClass *scrap=[[ScrapingClass alloc]init];
                       TrnObj=   [scrap train_information: [NSString stringWithFormat:@"http://erail.in/Rail/getPNRStatusAsynch.aspx?Data=%@",pnr_no]];

                       //  NSLog(@"NAME..... %@  NO    %@    Date %@  Class        %@   \ndes==%@\n %@     \n   Dep time %@     Arr time %@   PASSENGER%@      Class       %@", TrnObj.TrainName,TrnObj.TrainNumber,TrnObj.TrainDate,TrnObj.TrainBokingSts,TrnObj.TrainBoarding,TrnObj.TrainDestination,TrnObj.TrainDepTime,TrnObj.TrainArrivalTime,TrnObj.trainTicDictionary,TrnObj.TrainClass);

                       dispatch_sync(dispatch_get_main_queue(), ^{
                           //If self.image is atomic (not declared with nonatomic)
                           // you could have set it directly above
                           [activityIndicator stopAnimating];

                           if ([TrnObj.TrainNumber length]>3){


//**********************                ************************
                               [dbSingleton() createEditableCopyOfDatabaseIfNeeded];
                               if ([dbSingleton()  checkpnrEsistence:pnr_no]>0)
                               {
    //                      [dbSingleton()  deletePnr:pnr_no];
                                   [dbSingleton()  update_Pnr:TrnObj.TrainName trainNumber:TrnObj.TrainNumber chartPrepared:TrnObj.TrainChart className:TrnObj.TrainClass alight_code:TrnObj.TrainDestinationCode alight_name:TrnObj.TrainDestination board_code:TrnObj.TrainBoardingCode board_name:TrnObj.TrainBoarding from_code:TrnObj.TrainDestinationCode from_name:TrnObj.TrainBoarding   tr_date:TrnObj.TrainDate to_code:TrnObj.TrainDestinationCode to_name:TrnObj.TrainDestination BordTime:TrnObj.TrainDepTime FromTime:TrnObj.TrainDepTime ToTime:TrnObj.TrainArrivalTime PNR_number:pnr_no];

                               }

                               [activityIndicator stopAnimating];
                               NSArray *seatdetails=[TrnObj.trainTicDictionary objectForKey:@"passengers"];

            NSLog(@"SCRAPING  self.seat_details %@",self.seat_details);

                               for(int i=0;i