如何在sonata_type_collection中获取未映射字段?

我正在使用Sonata Admin与Symfony 2.8.9。

两个实体:Skill和SkillStep。技能与SkillSteps有一对多的关系。

Skill管理员有一个sonata_type_collection字段，它嵌入了多个SkillStep管理员。

每个SkillStep管理员都有一个未映射的文本字段，称为"data"。它不直接映射到SkillStep实体中的任何值。

当用户保存或更新技能时，我想根据sonata_type_collection中每个SkillStep管理员的"数据"字段的输入运行任意代码。

这样做的明显位置是SkillStep管理中的prePersist()和preUpdate()。然而,

当将一个Admin嵌入到另一个Admin中时，例如使用sonata_type_admin字段类型，子Admin的钩子不会被触发。

在保存顶级实体时，我如何使用sonata_type_collection嵌入的admins的未映射字段?这些未映射的字段与它们所在的管理对象相关联是很重要的。

相关代码:

# Entity/Skill.php
class Skill {
    /**
     * @ORM'OneToMany(targetEntity="SkillStep", mappedBy="skill")
     */
    private $steps;
    // ...
}

---

# Entity/SkillStep.php
class SkillStep {
    /**
     * @ORM'ManyToOne(targetEntity="Skill")
     * @ORM'JoinColumn(name="skill_id", referencedColumnName="id")
     **/
    protected $skill;
    // ..
}

---

# Admin/SkillAdmin.php
class SkillAdmin extends Admin 
{
    // Fields to be shown on create/edit forms
    protected function configureFormFields(FormMapper $formMapper) {
        $formMapper
            ->add('name')
            ->add('steps', 'sonata_type_collection',
                ['required' => false, 'label' => 'Manage the skill steps'],
                ['edit'=>'inline','inline'=>'standard']
            )
        ;
    }
}

---

# Admin/SkillStepAdmin.php
class SkillStepAdmin extends Admin 
{
    // Fields to be shown on create/edit forms
    protected function configureFormFields(FormMapper $formMapper) {
        $formMapper
            ->add('name')
            ->add('route')
            ->add('data', 'textarea', [
                'mapped' => false,
                'data' => $step_data,
            ])
        ;
    }
    // Before a new skill step is saved
    public function prePersist($skill_step) {
        // THIS IS NEVER CALLED BECAUSE THIS ADMIN IS EMBEDDED
    }
    // Before an existing skill step is updated
    public function preUpdate($skill_step) {
        // THIS IS NEVER CALLED BECAUSE THIS ADMIN IS EMBEDDED
    }
}

# Admin/SkillAdmin.php    
private function getStepAdmin() {
    return $this->getConfigurationPool()
                ->getAdminByAdminCode('skill_step_admin_service_id');
}
public function prePersist($skill)
{
    foreach ($skill->getSteps() as $step) {
        $this->getStepAdmin->prePersist($step); 
    }
}
public function preUpdate($skill)
{
    foreach ($skill->getSteps() as $step) {
        $this->getStepAdmin->preUpdate($step); 
    }
}

$myUnmappedData = $form->get('steps')->get($key)->get('SkillStep')->get('unmappedField')->getData();

# Admin/SkillAdmin.php    
private function getStepAdmin() {
    return $this->getConfigurationPool()
                ->getAdminByAdminCode('skill_step_admin_service_id');
}
public function prePersist($skill)
{
    
    foreach ($skill->getSteps() as $key => $step) {
        #access to unmapped form field
        $myUnmappedData = $form->get('steps')->get($key)->get('SkillStep')->get('unmappedField')->getData();
        $this->getStepAdmin->publicFunctionToManageMyData($step, $myUnmappedData); 
    }
}