title: how to check for null object returned in xcode
body: <p>I have a NULL object returned from a JSON query string and I don't know how to check for it in an If statement. My syntax is below but I still don't seem to be able to trap for the <code>NULL</code> class (i.e., if nothing is returned then no text variable can be set therefore it MUST be a <code>NULL</code> class?), anyway, I need to check that the <code>@"BillingStreet"</code> has something in it and if not to avoid processing it (else the app crashes as it tries to set nothing to the text value of one of the <code>fields</code> in the <code>VC</code>):</p>
  
  <pre><code>- (void) tableView: (UITableView *)itemTableView didSelectRowAtIndexPath: (NSIndexPath *)indexPath{
      NSDictionary *obj = [self.dataCustomerDetailRows objectAtIndex:indexPath.row];
      NSString *text = [obj objectForKey:@"BillingStreet"] == nil ? @"0" : [obj objectForKey:@"BillingStreet"];
      NSLog(@"%@",text);
      if (text.class == NULL){
      } else {
          NSLog(@"no street");
          self.labelCustomerAddress.text = [obj objectForKey:@"BillingStreet"];
      }
  }
  </code></pre>