Question

I’m using Doctrine 2.2.0 together with Codeigniter. I’m new to Doctrine (or to ORM in general).

I’m setting up entity and proxy classes based on YAML files which works fine. I do have problems in reflecting a polymorphic association in my DB in my Doctrine classes. I’m looking for a concrete example on how to implement the following polymorphic association in Doctrine.

In my DB I have a table called products. Depending on the value of field object_type and object_id I want to relate either to a record in the table videos or the table cars (I simplified it here). I want to keep both product types in 2 separate table because one has nothing to do with the other and both tables relate to other tables.

I took a look at the Doctrine Inheritance documentation and other examples, but it doesn’t seem to help me. If possible I want to avoid adding the columns description and price to the tables videos and cars.

Many thanks!

|Table: products                                      |
|-----------------------------------------------------|
| ID | description | price  | object_type | object_id |
|-----------------------------------------------------|
| 1  | A video     | 20.00  | video       | 12        |
| 2  | A car       | 159.00 | car         | 5         |

|Table: videos                               |
|--------------------------------------------|
| ID | filename     | artist_id | date       |
|--------------------------------------------|
| 12 | somename.mp4 | 189       | 2011-02-15 |

|Table: cars                   |
|------------------------------|
| ID | brand_id | model | year |
|------------------------------|
| 5  | 17       | astra | 2010 |

Answer 1

Found the solution myself. I’ve listed below the different steps I’ve done. This answer is very big, but I tried to be as complete as possible.

The most important things are in the Product YAML files inheritanceType: JOINED, discriminatorColumn:, discriminatorMap: and the Video and Car entity classes class Video extends Product, class Car extends Product.

1) DB Schema

CREATE TABLE IF NOT EXISTS `artists` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB;

CREATE TABLE IF NOT EXISTS `brands` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB;

CREATE TABLE IF NOT EXISTS `cars` (
  `id` int(11) NOT NULL,
  `model` varchar(255) NOT NULL,
  `release_date` date NOT NULL,
  `brand_id` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB;

CREATE TABLE IF NOT EXISTS `products` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `description` varchar(255) NOT NULL,
  `price` double NOT NULL,
  `object_type` varchar(255) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB;

CREATE TABLE IF NOT EXISTS `videos` (
  `id` int(11) NOT NULL,
  `file_name` varchar(255) NOT NULL,
  `release_date` date NOT NULL,
  `artist_id` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB;

2) Doctrine YAML files (from which you need to create the Entity and proxy classes)

Entities.Artist.dcm.yml

Entities\Artist:
    type: entity
    table: artists
    id:
        id:
            type: integer
            primary: true
            notnull: true
            generator:
                strategy: AUTO
    fields:
        name:
            type: string(255)
            notnull: true
    oneToMany:
        videos:
            targetEntity: Video
            mappedBy: artist
    options:
        charset: utf8
        type: InnoDB

Entities.Brand.dcm.yml

Entities\Brand:
    type: entity
    table: brands
    id:
        id:
            type: integer
            primary: true
            notnull: true
            generator:
                strategy: AUTO
    fields:
        name:
            type: string(255)
            notnull: true
    oneToMany:
        cars:
            targetEntity: Car
            mappedBy: brand
    options:
        charset: utf8
        type: InnoDB

Entities.Car.dcm.yml

Entities\Car:
    type: entity
    table: cars
    fields:
        model:
            type: string
            notnull: true
        release_date:
            type: date
            notnull: true
    oneToOne: #unidirectional    
        brand:
            targetEntity: Brand
            joinColumns:
                brand_id:
                    referencedColumnName: id
    options:
        charset: utf8
        type: InnoDB

Entities.Product.dcm.yml

Entities\Product:
    type: entity
    table: products
    id:
        id:
            type: string
            primary: true
            notnull: true
            generator:
                strategy: AUTO
    fields:
        description:
            type: string(255)
            notnull: true
        price:
            type: decimal
            notnull: true
    inheritanceType: JOINED
    discriminatorColumn:
        name: object_type
        type: string
        length: 255
    discriminatorMap:
        video: Video
        car: Car
    options:
        charset: utf8
        type: InnoDB

Entities.Video.dcm.yml

Entities\Video:
    type: entity
    table: videos
    fields:
        file_name:
            type: string
            notnull: true
        release_date:
            type: date
            notnull: true
    oneToOne: #unidirectional    
        artist:
            targetEntity: Artist
            joinColumns:
                artist_id:
                    referencedColumnName: id
    options:
        charset: utf8
        type: InnoDB

3) Create Entity and Proxy classes

I use CodeIgniter. I’ve used Joel Verhagen’s excellent guide

!! It’s important you extend Video and Car with Product – See below !!

This results in the following Entity classes

Artist.php

namespace Entities;

use Doctrine\ORM\Mapping as ORM;

/**
 * Entities\Artist
 *
 * @ORM\Table(name="artists")
 * @ORM\Entity
 */
class Artist
{
    /**
     * @var integer $id
     *
     * @ORM\Column(name="id", type="integer")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="IDENTITY")
     */
    private $id;

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

    /**
     * @var \Doctrine\Common\Collections\ArrayCollection
     *
     * @ORM\OneToMany(targetEntity="Entities\Video", mappedBy="artist")
     */
    private $videos;

    public function __construct()
    {
        $this->videos = new \Doctrine\Common\Collections\ArrayCollection();
    }

    /**
     * Get id
     *
     * @return integer 
     */
    public function getId()
    {
        return $this->id;
    }

    /**
     * Set name
     *
     * @param string $name
     * @return Artist
     */
    public function setName($name)
    {
        $this->name = $name;
        return $this;
    }

    /**
     * Get name
     *
     * @return string 
     */
    public function getName()
    {
        return $this->name;
    }

    /**
     * Add videos
     *
     * @param Entities\Video $videos
     */
    public function addVideo(\Entities\Video $videos)
    {
        $this->videos[] = $videos;
    }

    /**
     * Get videos
     *
     * @return Doctrine\Common\Collections\Collection 
     */
    public function getVideos()
    {
        return $this->videos;
    }
}

Brand.php

namespace Entities;

use Doctrine\ORM\Mapping as ORM;

/**
 * Entities\Brand
 *
 * @ORM\Table(name="brands")
 * @ORM\Entity
 */
class Brand
{
    /**
     * @var integer $id
     *
     * @ORM\Column(name="id", type="integer")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="IDENTITY")
     */
    private $id;

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

    /**
     * @var \Doctrine\Common\Collections\ArrayCollection
     *
     * @ORM\OneToMany(targetEntity="Entities\Car", mappedBy="brand")
     */
    private $cars;

    public function __construct()
    {
        $this->cars = new \Doctrine\Common\Collections\ArrayCollection();
    }

    /**
     * Get id
     *
     * @return integer 
     */
    public function getId()
    {
        return $this->id;
    }

    /**
     * Set name
     *
     * @param string $name
     * @return Brand
     */
    public function setName($name)
    {
        $this->name = $name;
        return $this;
    }

    /**
     * Get name
     *
     * @return string 
     */
    public function getName()
    {
        return $this->name;
    }

    /**
     * Add cars
     *
     * @param Entities\Car $cars
     */
    public function addCar(\Entities\Car $cars)
    {
        $this->cars[] = $cars;
    }

    /**
     * Get cars
     *
     * @return Doctrine\Common\Collections\Collection 
     */
    public function getCars()
    {
        return $this->cars;
    }
}

Car.php

namespace Entities;

use Doctrine\ORM\Mapping as ORM;

/**
 * Entities\Car
 *
 * @ORM\Table(name="cars")
 * @ORM\Entity
 */
class Car extends Product //Important that Car extends Product
{
    /**
     * @var string $model
     *
     * @ORM\Column(name="model", type="string")
     */
    private $model;

    /**
     * @var date $release_date
     *
     * @ORM\Column(name="release_date", type="date")
     */
    private $release_date;

    /**
     * @var Entities\Brand
     *
     * @ORM\OneToOne(targetEntity="Entities\Brand")
     * @ORM\JoinColumns({
     *   @ORM\JoinColumn(name="brand_id", referencedColumnName="id", unique=true)
     * })
     */
    private $brand;


    /**
     * Set model
     *
     * @param string $model
     * @return Car
     */
    public function setModel($model)
    {
        $this->model = $model;
        return $this;
    }

    /**
     * Get model
     *
     * @return string 
     */
    public function getModel()
    {
        return $this->model;
    }

    /**
     * Set release_date
     *
     * @param date $releaseDate
     * @return Car
     */
    public function setReleaseDate($releaseDate)
    {
        $this->release_date = $releaseDate;
        return $this;
    }

    /**
     * Get release_date
     *
     * @return date 
     */
    public function getReleaseDate()
    {
        return $this->release_date;
    }

    /**
     * Set brand
     *
     * @param Entities\Brand $brand
     * @return Car
     */
    public function setBrand(\Entities\Brand $brand = null)
    {
        $this->brand = $brand;
        return $this;
    }

    /**
     * Get brand
     *
     * @return Entities\Brand 
     */
    public function getBrand()
    {
        return $this->brand;
    }
}

Product.php

namespace Entities;

use Doctrine\ORM\Mapping as ORM;

/**
 * Entities\Product
 *
 * @ORM\Table(name="products")
 * @ORM\InheritanceType("JOINED")
 * @ORM\DiscriminatorColumn(name="", type="", length=)
 * @ORM\DiscriminatorMap({"video" = "Entities\Video", "car" = "Entities\Car"})
 * @ORM\Entity
 */
class Product
{
    /**
     * @var string $id
     *
     * @ORM\Column(name="id", type="string")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="IDENTITY")
     */
    private $id;

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

    /**
     * @var decimal $price
     *
     * @ORM\Column(name="price", type="decimal")
     */
    private $price;


    /**
     * Get id
     *
     * @return string 
     */
    public function getId()
    {
        return $this->id;
    }

    /**
     * Set description
     *
     * @param string $description
     * @return Product
     */
    public function setDescription($description)
    {
        $this->description = $description;
        return $this;
    }

    /**
     * Get description
     *
     * @return string 
     */
    public function getDescription()
    {
        return $this->description;
    }

    /**
     * Set price
     *
     * @param decimal $price
     * @return Product
     */
    public function setPrice($price)
    {
        $this->price = $price;
        return $this;
    }

    /**
     * Get price
     *
     * @return decimal 
     */
    public function getPrice()
    {
        return $this->price;
    }
}

Video.php

namespace Entities;

use Doctrine\ORM\Mapping as ORM;

/**
 * Entities\Video
 *
 * @ORM\Table(name="videos")
 * @ORM\Entity
 */
class Video extends Product //Important that Video extends Product
{
    /**
     * @var string $file_name
     *
     * @ORM\Column(name="file_name", type="string")
     */
    private $file_name;

    /**
     * @var date $release_date
     *
     * @ORM\Column(name="release_date", type="date")
     */
    private $release_date;

    /**
     * @var Entities\Artist
     *
     * @ORM\OneToOne(targetEntity="Entities\Artist")
     * @ORM\JoinColumns({
     *   @ORM\JoinColumn(name="artist_id", referencedColumnName="id", unique=true)
     * })
     */
    private $artist;


    /**
     * Set file_name
     *
     * @param string $fileName
     * @return Video
     */
    public function setFileName($fileName)
    {
        $this->file_name = $fileName;
        return $this;
    }

    /**
     * Get file_name
     *
     * @return string 
     */
    public function getFileName()
    {
        return $this->file_name;
    }

    /**
     * Set release_date
     *
     * @param date $releaseDate
     * @return Video
     */
    public function setReleaseDate($releaseDate)
    {
        $this->release_date = $releaseDate;
        return $this;
    }

    /**
     * Get release_date
     *
     * @return date 
     */
    public function getReleaseDate()
    {
        return $this->release_date;
    }

    /**
     * Set artist
     *
     * @param Entities\Artist $artist
     * @return Video
     */
    public function setArtist(\Entities\Artist $artist = null)
    {
        $this->artist = $artist;
        return $this;
    }

    /**
     * Get artist
     *
     * @return Entities\Artist 
     */
    public function getArtist()
    {
        return $this->artist;
    }
}

3) Creating a new Car and a new Video

This is what goes in my CodeIgniter controller. The code presumes you’ve created an artist with the name Metallica and a brand with the name Ford.

public function createVideo()
{
    //Instantiate new Entities\Video object
    $video = new Entities\Video;

    //Since it extends Entities\Product you can set the common Product properties
    $video->setDescription('This is a Metallica clip');
    $video->setPrice(19.95);

    //Setting the custom Video properties
    $artist = $this->doctrine->em->getRepository('Entities\Artist')->findOneBy(array('name' => 'Metallica'));
    $video->setArtist($artist);
    $video->setReleaseDate(new DateTime());
    $video->setFileName('metallica.mp4');

    //Save
    $this->doctrine->em->persist($video);
    $this->doctrine->em->flush();
}

public function createCar()
{
    //Instantiate new Entities\Car object
    $car = new Entities\Car;

    //Since it extends Entities\Product you can set the common Product properties
    $car->setDescription('This is Ford Mondeo of 2011');
    $car->setPrice(19.95);

    //Setting the custom Car properties
    $brand = $this->doctrine->em->getRepository('Entities\Brand')->findOneBy(array('name' => 'Ford'));
    $car->setBrand($brand);
    $car->setReleaseDate(DateTime::createFromFormat('Y-m-d', '2011-11-15'));
    $car->setModel('Mondeo');

    //Save
    $this->doctrine->em->persist($car);
    $this->doctrine->em->flush();
}

4) Extracting all products

An example on how to extract all Products

public function extractAllProducts()
{
    $products = $this->doctrine->em->getRepository('Entities\Product')->findAll();
    foreach($products as $product)
    {
        printf('%s for € %s<br />', $product->getDescription(), $product->getPrice());
    }
}

This results into

This is a Metallica clip for € 19.95
This is Ford Mondeo of 2011 for € 19.95

An example onn how to extract all Videos

public function extractAllVideos()
{
    $videos = $this->doctrine->em->getRepository('Entities\Video')->findAll();
    foreach($videos as $video)
    {
        printf('%s, released %s for € %s<br />', $video->getDescription(),  $video->getReleaseDate()->format('Y'), $video->getPrice());
    }
}

This results into

This is a Metallica clip, released 2012 for € 19.95