Doctrine multiple level inheritance mapping

Question

I have four types of products which I would like to map to a Doctrine ORM structure on a MySQL RDBMS. The products are PrepaidProduct , PostpaidProduct , MobilePrepaidProduct , MobilePostpaidProduct with the following structure:

abstract class Product {
    /**
     * @ORM\Column(type="integer")
     */
    private $price;

    ...
}

class PrepaidProduct extends Product {
    /**
     * @ORM\Column(type="integer")
     */
    private $credit;

    /**
     * @ORM\OneToMany(targetEntity="PrepaidDiscount")
     */
    private $prepaidDiscounts;
}

class PostpaidProduct extends Product {
    /**
     * @ORM\OneToMany(targetEntity="BundleMapping")
     */
    private $bundleMappings;
}

class MobilePrepaidProduct extends PrepaidProduct {
    /**
     * @ORM\ManyToOne(targetEntity="Device")
     */
    private $device;
}

class MobilePostpaidProduct extends PostpaidProduct {
    /**
     * @ORM\ManyToOne(targetEntity="Device")
     */
    private $device;
}

The main idea is that I would like to use a service (factory) that will use the basic class structure of the PostpaidProduct class to create a structure of the corresponding bundle mapping, so I think I would need this as a mapped super class.

In my opinion the way to go would be to have two separate tables, one for PostpaidProduct and one for PrepaidProduct , and have a Single Table Inheritance on those for MobilePostpaidProduct / PostpaidProduct and MobilePrepaidProduct / PrepaidProduct .

What do you guys think? Any thoughts on best way to model this?

Answer 1

If you are using a RDBMS layer [MySQL, Postgre] as I think, your proposal is the best choice in my opinion.

If subclasses have * little more attributes, possibly relationships most of all, you are actually promoting composition and your data representation won't be sparse [ie you won't have many empty fields in the main table].

On the other hand, if you want to stick with composition only [which is more advisable in most cases] - is $device the only additional relationship in Mobile classes? If so, you could write a findAllMobileProducts method in your repository class that would return every product where device is not null, and so on.