ZF2 ObjectMultiCheckbox for OneToMany，doctrine hydrator和DB storage

I'm using ZF2, Doctrine and Doctrine Hydrator. I've the following tables

• TOURS (with one field named 'tour type' - OneToMany association - rendered by ObjectMultiCheckbox and showing a list of tour type from TOURTYPE table)
• TOURTYPES (a list of tour types)

I've a "Tours" Class and "TourTypes" Class and the TourFormFieldset with the following field:

$this->add( array(
        'type'      => 'DoctrineModule\Form\Element\ObjectMultiCheckbox',
        'name'      => 'tourtype',
        'options'   => array(
            'object_manager'    =>  $this->getObjectManager(),
            'target_class'      =>  'Tours\Entity\TourType',
            'property'          =>  'title',
            'label'             =>  'Tour Type'
        )   
     )
   );

I can display a list of tourtypes checkbox in the tour editing view, but i don't know how to store a retrieve a collection of tour types selected.