Ojs\JournalBundle\Entity\Subject::addChild PHP 메소드

    public function addChild(Subject $child)
    {
        if (!$this->children->contains($child)) {
            $this->children->add($child);
            $child->setParent($this);
        }
    }

 /**
  * @param Subject|null $parent
  * @return Subject
  */
 public function setParent(Subject $parent = null)
 {
     $this->parent = $parent;
     if (!$parent) {
         $parent->addChild($this);
     }
     return $this;
 }