Requesting and parsing json data from rails app in objective-c

listing.c

+(NSMutableArray *) loadRemoteListings {
    
    NSMutableArray *listings = [NSMutableArray arrayWithCapacity:20];
    
    NSURL *url = [[NSURL alloc] initWithString:@"http://localhost:3000"];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
    [request setValue:@"application/json" forHTTPHeaderField:@"Accept"];
    
    NSURLResponse *response;
    NSError *error;
    NSData *response_data = [NSURLConnection sendSynchronousRequest:request 
                                                  returningResponse:&response 
                                                              error:&error];
    NSDictionary* json = [NSJSONSerialization 
                          JSONObjectWithData:response_data
                          options:kNilOptions 
                          error:&error]; 
    
    for ( NSDictionary *list in json ) {
        Listing *listing = [[Listing alloc] init];
        listing.details = [list valueForKey:@"details"];
        listing.description= [list valueForKey:@"description"];
        [listings addObject:listing]; 
    }
    
    return listings;
}