gistfile1.m

    NSURL* url = [NSURL URLWithString:[_urlString stringByAppendingString:@"messages"]];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:60.0];
    
    void (^handler)(NSURLResponse* response, NSData* data, NSError* error);
    handler = ^(NSURLResponse* response, NSData* data, NSError* error){
        NSString* result = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
        
        if (data == nil) {
            NSLog(@"Connection failed! Error - %@ %@",
                  [error localizedDescription],
                  [[error userInfo] objectForKey:NSURLErrorFailingURLStringErrorKey]);
            return;
        }
        
        NSJSONSerialization* _jsonObject = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&error];
        
        if (_jsonObject == nil) {
            NSLog(@"JSON data parsing failed! Error - %@ %@",
                  [error localizedDescription],
                  [[error userInfo] objectForKey:NSURLErrorFailingURLStringErrorKey]);
        self._dataTextView.text = [error description];
            return;
        }
    };
    
    [NSURLConnection sendAsynchronousRequest:request
                                       queue:[NSOperationQueue currentQueue]
                           completionHandler:handler];