如何扩展具有内部关系的实体？

Question

I hope you will be able to help because I have been searching for a few days now. I have a class called "Attributes". In it, there is a parentId which reference a other entry of Attributes .

I want to extend the entity "Attributes" as "Products" with a few extra fields. All the fields are being extended except for the parentId relation.

When I add parent to Products with getter and setter I get a error:

`"Compile Error: Declaration of Products::setParent(?Attributes $parent): Products must be compatible with Attributes::setParent(?Attributes $parent)
  : Attributes"`

I have tried a standalone Entity Products with all the fields but the relationship to Attributes causes database relation issues. And it is an extension of Attributes .

Tried different kinds of getters and setters and leaving it out to be extended from the parent.

Have been searching the web for a answer but have not seen inheritance with a internal relationship.

Attributes class:

namespace App\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity()
 */
class Attributes
{
    /**
     * @ORM\Id()
     * @ORM\Column(type="string", length=255)
     */
    private $id;

    /**
     * @ORM\Column(type="string", length=255)
     */
    private $val;

    /**
     * @ORM\Column(type="string", length=255)
     */
    private $category;

    /**
     * @ORM\ManyToOne(targetEntity="App\Entity\Attributes")
     * @ORM\JoinColumn(name="parent_id", referencedColumnName="id")
     */
    private $parent;
}

Products class:

namespace App\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity()
 */
class Products extends Attributes
{
   /**
     * @ORM\Column(type="string", length=255)
     */
    private $newField1;

    /**
     * @ORM\Column(type="string", length=255)
     */
    private $newField2;
}

I would like to know why the internal relationship "Parent" isn't extended and I would love to know how to get the parentId in the extended class.

Answer 1

Your parent setters seems to be like this:

/** Product **/
public function setParent(?Attributes $parent): Products
{
   $this->parent = $parent;

   return $this;
}
/** Attribute **/
public function setParent(?Attributes $parent)
{
   $this->parent = $parent;

   return $this;
}

You can fix it simply by replacing :Products by :Attributes at the end of setParent line in product class.

But you should use an interface

interface AttributeInterface 
{
    public function setParent(?AttributeInterface $parent): AttributeInterface
}

and each of your entity should implement it:

Attribute:

namespace App\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity()
 */
class Attributes implements AttributesInterface
{
    /*****/
    public function setParent(?AttributeInterface $parent): AttributeInterface
    {
        $this->parent = $parent;

        return $this;
    }
}

Product:

namespace App\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity()
 */
class Products extends Attributes implements AttributesInterface
{
   /*****/
}