ios - 如何等到 NSURLResponse 被处理后再循环迭代？

Question

我正在尝试在发出后续请求之前处理每个请求的数据。这里有两个方法，第二个方法是在第一个方法中使用 dispatch_semaphore 调用的，以确保请求完成，但是，这不会等到响应实际被接收/处理后才会出现。这会导致正在制作的图表没有按正确的顺序制作，有时文件夹名称会显示错误的数据。

- (void)load:(NSData*)data completionHandler:(void(^)(NSURLResponse *response, NSData *data, NSError *error))handler

{
    NSString *s = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

    NSLog(@"Loading... %@", s);

    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];

    NSURLConnection *urlConnection = [[NSURLConnection alloc] initWithRequest:request delegate:self]; //allows for SSL connections

    [request setHTTPMethod:@"POST"];

    [request setHTTPBody:data];

    NSOperationQueue *queue = [[NSOperationQueue alloc] init];

    [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue]

                           completionHandler:handler];

    [urlConnection start]; //start connection after request
}

//issue is occurring within this method
- (void)GetPOActivity:(NSString*)aliasname completionhandler:(void (^)(NSDictionary *, NSError *))handler;
{
    NSMutableDictionary *d = [[NSMutableDictionary alloc] init];

    [d setValue:interface forKey:@"interface"];

    [d setValue:@"GetDocsPerDay" forKey:@"method"];

    NSMutableDictionary *p = [[NSMutableDictionary alloc] init];

    NSString *cno = [[NSUserDefaults standardUserDefaults] objectForKey:@"cno"];

    [p setValue:aliasname forKey:@"aliasname"];

    [d setValue:p forKey:@"parameters"];

    NSData *data = [NSJSONSerialization dataWithJSONObject:d options:0 error:nil];

    [self load:data completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {

        NSLog(@"done");

        NSString *s = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

        NSLog(@"GetDocsPerDay RAW response = %@", s);

        //checks if data is null or server unavailable
        if (apiConditions)
        {
            dispatch_async(dispatch_get_main_queue(),
                           ^{
                               [hud hide:YES];
                               NSLog(@"data is NIL");
                           });
            [hud hide:YES];

        }
        else
        {
            //get values
            NSDictionary *d = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
            handler(d, error);
            NSMutableString *partnerString = d[@"Value"];
            NSArray *trArray = [[NSArray alloc] init];
            NSDictionary *trDict;
            trArray = partnerString;
            NSInteger arrayCount;

            arrayCount = trArray.count;

            for (int i = 0; i < arrayCount; i++)
            {
                trDict = trArray[i];
                //NSString *aliasNameString;
                //aliasNameString = test[@"AliasName"];


                if (d[@"Value"][i][@"folder"]!=nil)[folders addObject:d[@"Value"][i][@"folder"]];
                NSLog(@"folder is %d %@",i,d[@"Value"][i][@"folder"]);

                NSLog(@"%d",i);

            }

            dispatch_semaphore_t sema = dispatch_semaphore_create(folders.count);

            int i = 0;

            for (NSString *folder in folders)
            {
                NSCalendar *calendar = [NSCalendar currentCalendar];

                NSDate *date = [NSDate date];

                NSDateComponents *components = [[NSDateComponents alloc] init];

                [components setWeek:-1];

                NSDate *lastweek = [calendar dateByAddingComponents:components toDate:date options:0];

                NSLog(@"%@", lastweek);

                NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
                formatter.dateFormat = @"MM-dd-yyyy";
                NSString *today = [formatter stringFromDate:[NSDate date]];
                NSString *prevWeek = [formatter stringFromDate:lastweek];

                [self GetPOActivity2:aliasname startdate:prevWeek enddate:today document:folder completionhandler:^(NSDictionary *dictionary, NSError *error) {
                    dispatch_semaphore_signal(sema);
                    if (i == folders.count-1)
                    {
                        dispatch_async(dispatch_get_main_queue(),
                                       ^{
                                           //[hud hide:YES];
                                           [self initFakeData];
                                       });
                    }


                }];

                i++;
                dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER);
            }

            [hud hide:YES];

        }//end of else statement

    }];//end of block
}

 //final method called within loop
- (void)GetPOActivity2:(NSString*)aliasname startdate:(NSString*)startdate enddate:(NSString*)enddate document:(NSString*)document completionhandler:(void (^)(NSDictionary *, NSError *))handler;
{
    NSMutableDictionary *d = [[NSMutableDictionary alloc] init];

    [d setValue:interface forKey:@"interface"];

    [d setValue:@"GetDocsPerDay2" forKey:@"method"];

    NSMutableDictionary *p = [[NSMutableDictionary alloc] init];

    [p setValue:aliasname forKey:@"aliasname"];
    [p setValue:startdate forKey:@"startdate"];
    [p setValue:enddate forKey:@"enddate"];
    [p setValue:document forKey:@"document"];

    [d setValue:p forKey:@"parameters"];

    NSData *data = [NSJSONSerialization dataWithJSONObject:d options:0 error:nil];

    [self load:data completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {

        NSLog(@"done");

        NSString *s = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

        NSLog(@"GetDocsPerDay2 RAW response = %@", s);

        //checks if data is null or server unavailable
        if (apiConditions)
        {
            dispatch_async(dispatch_get_main_queue(),
                           ^{
                               [hud hide:YES];
                               NSLog(@"data is NIL");
                           });
            [hud hide:YES];

        }
        else
        {
            //get values
            NSDictionary *d = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
            handler(d, error);
            NSMutableString *partnerString = d[@"Value"];
            NSArray *trArray = [[NSArray alloc] init];
            NSDictionary *trDict;
            trArray = partnerString;
            NSInteger arrayCount;

            arrayCount = trArray.count;

            JBdataCount = arrayCount;
            for (int i = 0; i < arrayCount; i++)
            {
                trDict = trArray[i];

                if (d[@"Value"][i][@"data"]!=nil)
                {
                    [dataArray addObject:d[@"Value"][i][@"data"]];

                    NSString *tempMonth = @""; //used for month name
                    tempMonth = [self convertMonthToString:d[@"Value"][i][@"month"]];

                    [dateArray addObject:[NSString stringWithFormat:@"%@, %@ %@",tempMonth,d[@"Value"][i][@"day"],d[@"Value"][i][@"year"]]];
                }
                NSLog(@"data is %d %@",i,d[@"Value"][i][@"data"]);
                NSLog(@"%d",i);

            }
            [hud hide:YES];

        }//end of else statement

    }];//end of block
}

Answer 1

老实说，这里最好的解决方案是使用类似 PromiseKit 的东西.