How do I map this relationship? - symfony

Question

I'm having trouble mapping this relationship in Doctrine. I have a UseCase, which has many UseCaseSteps. A UseCaseStep has many sub-steps, which is a OneToMany on UseCaseStep. Here's the pertinent code I have atm:
/**
* UseCase
*
* #ORM\Table(name="use_cases")
* #ORM\Entity(repositoryClass="DesignCase\Bundle\Bundle\Entity\UseCaseRepository")
*/
class UseCase
{
/**
* #var ArrayCollection
*
* #ORM\ManyToMany(targetEntity="Actor", inversedBy="use_cases", cascade={"persist", "remove"})
* #ORM\JoinTable(name="actors_use_cases")
*/
private $actors;
/**
* #var ArrayCollection
*
* #ORM\OneToMany(targetEntity="UseCaseStep", mappedBy="useCase", cascade={"persist", "remove"})
* #ORM\OrderBy({"order" = "ASC"})
*/
private $steps;
}
/**
* UseCaseStep
*
* #ORM\Table(name="use_case_steps")
* #ORM\Entity(repositoryClass="DesignCase\Bundle\Bundle\Entity\UseCaseStepRepository")
*/
class UseCaseStep
{
/**
* #var integer
*
* #ORM\ManyToOne(targetEntity="UseCase")
*/
private $useCase;
/**
* #var ArrayCollection
*
* #ORM\OneToMany(targetEntity="UseCaseStep", mappedBy="parent", cascade={"persist", "remove"})
* #ORM\OrderBy({"order" = "ASC"})
*/
private $subSteps;
/**
* #var UseCase
*
* #ORM\ManyToOne(targetEntity="UseCase")
*/
private $useCaseReference;
/**
* #var UseCaseStep
*
* #ORM\ManyToOne(targetEntity="UseCaseStep")
* #ORM\JoinColumn(nullable=true)
*/
private $parent;
/**
* #var ArrayCollection
*
* #ORM\ManyToMany(targetEntity="BusinessRule", cascade={"persist", "remove"})
*/
private $businessRules;
}
That code isn't complete, but I think it has all the relevant information. What I want to do is create a new entity TestCase, which has many TestCaseSteps. A TestCase IS a UseCase with a little more information... same for TestCaseStep and UseCaseStep. IE, a TestCaseStep is a UseCaseStep with data input and expected output fields added to it. A user can create many TestCases from one UseCase.
I tried making UseCase and UseCaseStep #MappedSuperclass, but that doesn't have the desired effect. I get the obvious, "It is illegal to put an inverse side one-to-many or many-to-many association on mapped superclass" error. Plus, from the docs, I don't think that's the right approach anyway.
I'm having trouble wrapping my brain around it. Any thoughts? I hope I explained that well enough...

Answer 1

You have an issue there that is much more fundamental than Doctrine. You want to show inheritance in the database. For this approach there is no real correct solution. You could go with making an Entity TestCase that extends UseCase and overwrites the respective properties (need to make them protected) with another relation to TestCaseStep.
You do something similar with UseCaseStep and TestCaseStep. That way you have inheritance in the entities. Now you would have to make sure that you use another table and you end up with completely seperate entities database-wise. They just share the same properties in the entities but are seperate in database.
That approach would be in my opinion the easiest one to follow. Everything else seems to be very complicated as you cannot properly use one table with a different amount of properties for each entity. Each database table has a fixed set of properties that need to be reflected in an entity.
Another approach would surely be to just use the properties in the sub-entity that is used by this entity and create another relationship (many-to-one) between the TestCase and the UseCase or TestCaseStep and UseCaseStep respectively. But the latter approach isn't very easy and can end up being very complicated if you don't have a lot of knowledge about Doctrine, Symfony and databases in general.