Question

I’ve been reading over code samples and posts for days but I haven’t found a definitive way to post JSON data from my Core Data objects to a RESTful web service. There’s a TON of documentation about pulling the JSON from a web service but not so much about sending stuff back. Can anyone point me to a good example or post some code on how to do it? I’m using Core Data and I have the object I want to send back mapped to a Dictionary but I’m missing the code to send it to the service.

EDIT:

I ended up with the code below which looks right and runs without errors, but I get 0 bytes of data returned and my webservice doesn’t seem to be receiving the request. The JSON data looks good, the URL is correct, and I can hit the webservice and get JSON data back from it. The NSURLConnection delegate methods also fire as expected.

Is there anything I’m missing below?

- (void)SubmitSystems
{
    NSFetchRequest * allSystems = [[NSFetchRequest alloc] init];
    [allSystems setEntity:[NSEntityDescription entityForName:@"System" inManagedObjectContext:self.managedObjectContext]];
    NSError * error = nil;
    NSArray * systems = [self.managedObjectContext executeFetchRequest:allSystems error:&error];

    //error handling goes here
    //for (NSManagedObject * system in systems) {


    NSManagedObject *system = systems[2];

    NSString *entityString = @"System";
    NSString * serverString = [NSString stringWithFormat:@"%@%@", kWebServiceAddress, entityString];
    NSURL *url = [NSURL URLWithString:serverString];
    NSData* jsonData = [NSJSONSerialization dataWithJSONObject:[self jsonSystemDictionary:(System *)system] options:kNilOptions error:&error];

    //NSLog([[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding]); //debug only

    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy: NSURLRequestReloadIgnoringCacheData timeoutInterval: 30.f];

    [request setHTTPMethod:@"POST"];
    [request setValue:@"application/json" forHTTPHeaderField:@"Accept"];
    [request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
    [request setValue:[NSString stringWithFormat:@"%d", [jsonData length]] forHTTPHeaderField:@"Content-Length"];
    [request setHTTPBody: jsonData];

    self.urlConnection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
    [UIApplication sharedApplication].networkActivityIndicatorVisible = YES; 

//}
}

Answer 1

You’re going to need to NSMutableURLRequest. Using this, you can use setHTTPMethod and pass it the @"POST" string, and then use the attributes of your NSManagedObject to populate the URL, HTTPBody and/or HTTPHeader as needed.