小编Arn*_*oSr的帖子

我从事 Symfony 3.4 项目，我对特定的 Sonata Admin 案例有疑问，这是我的情况：

我有一个包含元素的课程实体：

/**
 * @ORM\OneToMany(targetEntity="App\Entity\Lessons\ElementLesson", mappedBy="lesson", cascade={"persist"})
 */
protected $elements;

Elements 是具有继承性的抽象类

/**
 * @ORM\Entity
 * @ORM\InheritanceType("JOINED")
 * @ORM\DiscriminatorColumn(name="discr", type="string")
 * @ORM\DiscriminatorMap({
 *     "element_lesson" = "ElementLesson",
 *     "popup_element_lesson" = "PopupElementLesson",
 *     "advice_element_lesson" = "AdviceElementLesson",
 *     "accordion_element_lesson" = "AccordionElementLesson",
 *     "title_element_lesson" = "TitleElementLesson",
 *     "text_element_lesson" = "TextElementLesson",
 *     "separator_element_lesson" = "SeparatorElementLesson"
 * })
 */
abstract class ElementLesson
{
    /**
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue
     */
    protected $id;

    /**
     * @ORM\ManyToOne(targetEntity="App\Entity\Lessons\Lesson", inversedBy="elements")
     * @ORM\JoinColumn(nullable=false, onDelete="CASCADE") …