dataTaskWithRequest 的 Objective-C 问题

Question

I have recently switched from sendSynchronousRequest to dataTaskWithRequest

with sendSynchronousRequest my method was working perfectly but when I switch to dataTaskWithRequest I get the following error:

error   NSURLError *    domain: @"NSURLErrorDomain" - code: 4294966096  0x15ee96c0

and

myError NSError *   domain: nil - code: 1684370017  0x26cce125

I don't understand why.

Here is the old code (commented out) and the new code:

/*-(NSDictionary *)GetProductionScheduleData:(NSString *)areaDescription
{
    NSString *areaDescriptionWSpaceCharacters = [areaDescription stringByReplacingOccurrencesOfString:@" " withString:@"%20"];
    NSString *requestString = [NSString stringWithFormat:@"%@?areaDescription=%@",kIP,areaDescriptionWSpaceCharacters];
    NSURL *JSONURL = [NSURL URLWithString:requestString];
    NSURLResponse* response = nil;
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:JSONURL];
    NSData* data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:nil];
    if(data == nil)
        return nil;
    NSError *myError;
    NSDictionary *productionSchedule = [[NSDictionary alloc]initWithDictionary:[NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&myError]];
    return productionSchedule;
}*/

-(void)GetProductionScheduleData:(NSString *)areaDescription Completetion:(void (^) (NSMutableDictionary * result,NSError * error))completion{

    NSString *areaDescriptionWSpaceCharacters = [areaDescription stringByReplacingOccurrencesOfString:@" " withString:@"%20"];
    NSString *requestString = [NSString stringWithFormat:@"%@?areaDescription=%@",kIP,areaDescriptionWSpaceCharacters];
    NSURL *JSONURL = [NSURL URLWithString:requestString];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:JSONURL];
    NSURLSession *session = [NSURLSession sharedSession];
    NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request
                                                completionHandler:^(NSData *data, NSURLResponse *response, NSError *error)
                                      {
                                          NSError *myError;
                                          NSMutableDictionary *productionSchedule = [[NSMutableDictionary alloc]initWithDictionary:[NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&myError]];

                                          completion(productionSchedule,myError);

                                      }];
    [dataTask resume];

}

Please Help! This was working with sendSynchronousRequest I am starting to dislike dataTaskWithRequest.

Answer 1

The NSURLSession code you have is correct, I confirmed with a valid URL.

You stopped checking to see if data is nil before attempting to JSON parse it. If you add that check back I bet you'll find that there is an error and data is in fact nil.

Change to:

NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
    // handle request error
    if (error) {
        completion(nil, error);
        return;
    }

    NSError *myError;
    NSMutableDictionary *productionSchedule = [[NSMutableDictionary alloc]initWithDictionary:[NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&myError]];
    completion(productionSchedule,myError);
}];

I would recommend also checking myError before attempting to set it to productionSchedule (which could also cause a crash).