大中央調度簡單的例子

Question

我是mac新手編程，我真的很驚訝大中央調度。我閱讀了這篇文章，看起來像是並行編程的完美解決方案。我使用POSIX線程並想要移至GCD。

我在Apple Developer Connection中看到了示例代碼，但它讓我非常困惑。我搜索了一個簡單的例子，用兩個線程開始，但我找不到它。

如何使用GCD做這個示例代碼？

#include <stdio.h>  /* standard I/O routines     */ 
#include <pthread.h>  /* pthread functions and data structures */ 

/* function to be executed by the new thread */ 
void* do_loop(void* data) 
{ 
int i;   /* counter, to print numbers */ 
int j;   /* counter, for delay  */ 
int me = *((int*)data);  /* thread identifying number */ 

for (i=0; i<10; i++) 
{ 
    for (j=0; j<500000; j++) /* delay loop */ 
    ; 
    printf("'%d' - Got '%d'\n", me, i); 
} 

/* terminate the thread */ 
pthread_exit(NULL); 
} 
void* th2(void* data) 
{ 
cout << "Thread nº 2" << endl; 
} 

int main(int argc, char* argv[]) 
{ 
int  thr_id;   /* thread ID for the newly created thread */ 
pthread_t p_thread1; 
pthread_t p_thread2;  /* thread's structure      */ 
int  a   = 1; /* thread 1 identifying number   */ 
int  b   = 2; /* thread 2 identifying number   */ 

/* create a new thread that will execute 'do_loop()' */ 
thr_id = pthread_create(&p_thread1, NULL, do_loop, (void*)&a); 
/* run 'do_loop()' in the main thread as well */ 
thr_id = pthread_create(&p_thread2, NULL, th2, (void*)&b); 


return 0; 
} 

在此先感謝

Answer 1

這將是這樣的：

// The block replaces your doLoop function, it basically does the same thing 
dispatch_block_t myBlock = ^{ 
    int i;   /* counter, to print numbers */ 
    int j;   /* counter, for delay  */ 

    dispatch_queue_t me = dispatch_get_current_queue();  /* The queue which currently runs this block */ 

    for (i=0; i<10; i++) 
    { 
     for (j=0; j<500000; j++) /* delay loop */ 
      ; 


     printf("'%s' - Got '%d'\n", dispatch_queue_get_label(me), i); // Print the name of the queue 
    } 
}; 


// Create two queues 
dispatch_queue_t queue1 = dispatch_queue_create("my.totally.unique.and.reverse.dns.identifier.1", NULL); 
dispatch_queue_t queue2 = dispatch_queue_create("my.totally.unique.and.reverse.dns.identifier.2", NULL); 

// Let both execute the block 
dispatch_async(queue1, myBlock); 
dispatch_async(queue2, myBlock); 

// And then release the queues because we are great citizens who care about memory 
dispatch_release(queue1); 
dispatch_release(queue2); 

Answer 2

只是包裝需要傳遞給dispatch_async()塊異步運行的代碼：

int main(int argc, char* argv[]) 
{ 
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), 
    ^{ 
     // This code runs asynchronously! 
     for (unsigned long long i = 0ULL; i < 100000000000ULL; i++) { 
      cout << i << endl; 
     } 
    }); 

    return 0; 
} 

請注意，在這個例子和你的例子中，應用程序實際上會立即返回，因爲你不要推遲從main()的回報。

Answer 3

-(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<seatdetails.count;i++) 
           { 
            NSString *seat_number=[NSString stringWithFormat:@"%@",[[seatdetails objectAtIndex:i] objectForKey:@"booking_status"]]; 
            NSString *seat_status=[NSString stringWithFormat:@"%@",[[seatdetails objectAtIndex:i] objectForKey:@"current_status"]]; 
            int roeid=[[[seatdetails objectAtIndex:i] objectForKey:@"rowid"] intValue]; 

            [dbSingleton() Update_Passenger:seat_number seat_status:seat_status pnr_number:pnr_no Row_ID:roeid]; 

           } 


//******************************  bord   ************************************ 
           NSMutableDictionary *resDicBor=[[NSMutableDictionary alloc]init]; 
           [resDicBor setValue:TrnObj.TrainBoardingCode forKey:@"code"]; 
           [resDicBor setValue:TrnObj.TrainBoarding forKey:@"name"]; 
           [resDicBor setValue:TrnObj.TrainDepTime forKey:@"time"]; 

           NSMutableDictionary *resB=[[NSMutableDictionary alloc]init]; 
           [resB setValue:resDicBor forKey:@"boarding_point"]; 
      NSLog(@"SCRAP resB.%@",resB); 

//*******************************  des    ******************************** 
           NSMutableDictionary *resDicDES=[[NSMutableDictionary alloc]init]; 
           [resDicDES setValue:TrnObj.TrainDestinationCode forKey:@"code"]; 
           [resDicDES setValue:TrnObj.TrainDestination forKey:@"name"]; 
           [resDicDES setValue:TrnObj.TrainArrivalTime forKey:@"time"]; 

           NSMutableDictionary *resD=[[NSMutableDictionary alloc]init]; 
           [resD setValue:resDicDES forKey:@"reservation_upto"]; 
     NSLog(@"SCRAP resD.%@",resD); 
//*******************************     ************************************* 
           NSMutableDictionary *resDicFro=[[NSMutableDictionary alloc]init]; 
           [resDicFro setValue:TrnObj.TrainBoardingCode forKey:@"code"]; 
           [resDicFro setValue:TrnObj.TrainBoarding forKey:@"name"]; 
           [resDicBor setValue:TrnObj.TrainDepTime forKey:@"time"]; 

           NSMutableDictionary *resF=[[NSMutableDictionary alloc]init]; 
           [resF setValue:resDicFro forKey:@"from_station"]; 
     NSLog(@"SCRAP resF.%@",resF); 




           self.travel_details=[[NSMutableArray alloc]init]; 
           [self.travel_details addObject:[resD objectForKey:@"reservation_upto"]]; 
           [self.travel_details addObject:[resB objectForKey:@"boarding_point"]]; 
           [self.travel_details addObject:[resF objectForKey:@"from_station"]]; 
     NSLog(@"SCRAP from_station....%@",[resF objectForKey:@"from_station"]); 
           self.seat_details=[TrnObj.trainTicDictionary objectForKey:@"passengers"]; 
     NSLog(@"SCRAP passengers....%@",TrnObj.trainTicDictionary); 
           self.pnr_detail_array=[[NSMutableArray alloc]init]; 
           [self.pnr_detail_array addObject:TrnObj.TrainNumber]; 
     NSLog(@"SCRAP train_number....%@",TrnObj.TrainNumber); 

           NSDateFormatter* Dformatter1 = [[NSDateFormatter alloc] init]; 
           [Dformatter1 setDateFormat:@"yyyy-MM-dd"]; 
           NSDateFormatter* Dformatter2 = [[NSDateFormatter alloc] init]; 
           [Dformatter2 setDateFormat:@"dd-MM-yyyy"]; 

           NSDate *TDate=[Dformatter1 dateFromString: TrnObj.TrainDate]; 
           NSString *trDat=[Dformatter2 stringFromDate:TDate]; 
           [self.pnr_detail_array addObject:trDat]; 

//  [self.pnr_detail_array addObject:[json objectForKey:@"doj"]]; 
     NSLog(@"SCRAP date....%@",trDat); 
           [self.pnr_detail_array addObject:TrnObj.TrainName]; 
           self.pnr_no=pnr_no; 

           if([TrnObj.TrainChart isEqualToString:@"N"]) 
           { 
            [self.pnr_detail_array addObject:@"Chart Not Prepared"]; 
           } else{ 
            [self.pnr_detail_array addObject:@"Chart Prepared"]; 
           } 
           [self.pnr_detail_array addObject:@""]; 
           [self.pnr_detail_array addObject:TrnObj.TrainClass]; 

       //*************update seat detail 







           str_seat_detail=@""; 
           for(int i=0;i<seat_details.count;i++) 
           { 
            str_seat_detail=[str_seat_detail stringByAppendingString:[NSString stringWithFormat:@"%@-%@\n",[[seat_details objectAtIndex:i] objectForKey:@"booking_status"],[[seat_details objectAtIndex:i] objectForKey:@"current_status"]]]; 
           } 

       NSLog(@" SCRAP str_seat_detail %@",str_seat_detail); 
           [table_view reloadData]; 

          }else{ 

          if (delegateObj.ScrapStatus==1) { 

          [self performSelector:@selector(getLoginData) withObject:nil afterDelay:0.0]; 
           UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:nil message:@"Trying Again" 
                        delegate:self cancelButtonTitle:nil 
                      otherButtonTitles:nil]; 
           [alertView show]; 
           [self performSelector:@selector(byeAlertView:) withObject:alertView afterDelay:0.5]; 
          }else{ 
           [activityIndicator stopAnimating]; 
           UIAlertView *alert =[[UIAlertView alloc]initWithTitle:nil message:@"Either the PNR is not generated or the travel date is in the past." delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil, nil]; 
           [alert show]; 
           } 
          } 

         }); 
        }); 

    }else 
    { 
     [activityIndicator stopAnimating]; 
     UIAlertView *alert =[[UIAlertView alloc]initWithTitle:@"Oops!" message:@" Try again later." delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil, nil]; 
     [alert show]; 
    } 

}