在cakephp3中添加查询字段

在cakephp3中，我似乎无法向查询结果添加字段。在cakephp2中，这个想法很简单，但由于我正在处理对象，这是不同的。我检查了以前的SE帖子，没有得到答案。它一定很简单，但我找不到。在这里，我试图添加一个自定义字段"距离"到结果集

$lessons=$this->Lessons->getLessonsDay($searchDate,$searchFirstName,$searchLastName,$searchSubject, $tutorIds);
         foreach( $lessons as $key => $item){
        //  debug($item); 
             $stlat=$item->student->address_lat;
             $stlong=$item->student->address_long;
             $tutlat=$item->tutor->address_lat;
             $tutlong=$item->tutor->address_long; 
              $dist=$this->calculate_distance( $stlat,$stlong,$tutlat,$tutlong);
              debug($dist);
             $lessons->distance= $dist; //no effect
             $lessons[$key]['distance']=$dist; //error
             $lessons[$key]['Lessons']['distance']=$dist; //Error: Cannot use object of type Cake'ORM'Query as array  
            }

如何添加到CakePHP3 ResultSet?

http://book.cakephp.org/3.0/en/orm/retrieving-data-and-resultsets.html checking-if-a-query-or-resultset-is-empty