问该实体的标识符生成策略要求在调用EntityManager#persist()之前填充ID字段

EN

class Interview {

    /**
     * @OneToMany(targetEntity="Question", mappedBy="question")
     */
    private $questions;

    public function __construct() {
        $this->questions = new ArrayCollection();
    }

    public function __toString() {
        return $this->id;
    }

    /**
     * @return Collection|Question[]
     */
    public function getQuestions() {
        return $this->questions;
    }

    /**
     * @ORM\Column(name="id", type="integer")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    private $id;
    ......
}

class Question {

    /**
     * @ManyToOne(targetEntity="Interview", inversedBy="interview")
     * @JoinColumn(name="interview_id", referencedColumnName="id")
     */
    private $interview;

    public function getInterview() {
        return $this->interview;
    }

    public function setInterview(Interview $interview) {
        $this->interview = $interview;
        return $this;
    }

    /**
     * @ORM\Column(type="integer")
     * @ORM\Id
     */
    private $interview_id;
    ......
}

if ($form->isSubmitted() && $form->isValid()) {

        $interview = new Interview();
        $question = new Question();

        $em->persist($interview);

        $question->setInterview($interview);
        $question->setTitle($request->get('title'));
        $em->persist($question);
        $em->flush();

        return $this->redirectToRoute('homepage');
}