Doctrine 2 many-to-many with MappedSuperclass in Zend framework 2 - php

Question

I am new to Doctrine2 and trying to create entities for the following DB structure:
I want to have all machine parts as an array in one attribute of the machine class. I tried this:
class Machine {
....
/**
* #var array
* #ORM\OneToMany(targetEntity="MachineHasPart", mappedBy="machine", cascade={"persist", "remove"}, orphanRemoval=TRUE)
*/
private $parts;
....
public function getParts () {
return array_map(
function ($machineHasPart) {
return $machineHasPart->getPart();
},
$this->parts->toArray()
);
}
}
Where MachineHasPart is a #MappedSuperclass for the intermediate entities/tables (like machineHasCylinder etc), but it failed with:
An exception occurred while executing 'SELECT FROM machineHasPart t0'.
Should I restructure my database to use ORM here? Or there is a solution for my case?

Answer 1

You cannot query a #MappedSuperClass. This is also mentioned in the Doctrine2 documentation in chapter 6.1. Mapped Superclasses:
A mapped superclass cannot be an entity, it is not query-able and persistent
This means you have to either change the target entity to something queryable or you have to make MachineHasPart to a entity and change to single table inheritance.
When I look at your database structure I would suggest changing your Machine entity to have three independent relationships for the parts. One for Belt, one for Cylinder and one for Gear.
Then instead of a generic getParts you will have three methods getBelts, getCylinders and getGears.
If that is really not what you want then you can leave a comment.
UPDATE
You can solve it also with class inheritance. First make a base class Part that is also an entity and use it in the other classes Belt, Cylinder and Gear:
Part:
<?php
namespace Machine\Entity;
use Doctrine\ORM\Mapping as ORM;
/**
* Part
*
* #ORM\Entity
* #ORM\Table("part")
* #ORM\InheritanceType("SINGLE_TABLE")
* #ORM\DiscriminatorColumn(name="discriminator", type="string")
* #ORM\DiscriminatorMap({
* "part" = "Part",
* "gear" = "Gear",
* "cylinder" = "Cylinder",
* "belt" = "Belt",
* })
* #property int $id
*/
class Part
{
/**
* #ORM\Id
* #ORM\Column(type="integer")
* #ORM\GeneratedValue(strategy="AUTO")
*/
protected $id;
/**
* #var Machine
* #ORM\ManyToOne(targetEntity="Machine\Entity\Machine", inversedBy="parts")
* #ORM\JoinColumn(name="machine_id", referencedColumnName="id", nullable=true)
*/
protected $machine;
/**
* Get id.
*
* #return int
*/
public function getId()
{
return $this->id;
}
/**
* Set id.
*
* #param int $id
* #return self
*/
public function setId($id)
{
$this->id = $id;
return $this;
}
//... add setters and getters for machine as normal ...
}
Extend this class in your other parts:
Belt:
<?php
namespace Machine\Entity;
/**
* Belt
*
* #ORM\Entity
*/
class Belt extends Part
{
}
Cylinder:
<?php
namespace Machine\Entity;
/**
* Cylinder
*
* #ORM\Entity
*/
class Cylinder extends Part
{
}
Gear:
<?php
namespace Machine\Entity;
/**
* Gear
*
* #ORM\Entity
*/
class Gear extends Part
{
}
Now in your machine relate to the parts like as follows.
Machine:
<?php
namespace Machine\Entity;
use Doctrine\ORM\Mapping as ORM;
use Doctrine\Common\Collections\Collection;
use Doctrine\Common\Collections\ArrayCollection;
/**
* Machine
*
* #ORM\Entity
* #ORM\Table("machine")
* #property int $id
*/
class Machine
{
/**
* #ORM\Id
* #ORM\Column(type="integer")
* #ORM\GeneratedValue(strategy="AUTO")
*/
protected $id;
/**
* Get id.
*
* #return int
*/
public function getId()
{
return $this->id;
}
/**
* Set id.
*
* #param int $id
* #return self
*/
public function setId($id)
{
$this->id = $id;
return $this;
}
/**
* #var Collection
* #ORM\OneToMany(targetEntity="Machine\Entity\Part", mappedBy="machine")
*/
protected $parts;
public function __constuct()
{
$parts = new ArrayCollection();
}
/**
*
* #return Collection
*/
public function getParts()
{
return $this->parts;
}
//... add setters and getters for parts as normal ...
}
Extend this class in your other parts:

Answer 2

Reading further in the Doctrine2 documentation in chapter 6.1. Mapped Superclasses (referred to by #Wilt):
... Furthermore Many-To-Many associations are only possible if the mapped superclass is only used in exactly one entity at the moment...
This means in this case the ORM mapping doesn't help. I cannot gather the data of all three entities MachineHasCylinder, MachineHasBelt and MachineHasGear through a MappedSupperclass at the same time.
I think using DQL or Native SQL is the only solution for this problem.