Symfony + Doctrine: Models and Inheritance

Question

I've separated my models from my entities. I have three models with corresponding entities: Review, RatedReview, and ScoredReview. Their relationship is ScoredReview extends RatedReview extends Review.

So for my models I have:

// Project/ReviewBundle/Model/Review.php

class Review
{
}

// Project/ReviewBundle/Model/RatedReview.php

class RatedReview extends Review
{
}

// Project/ReviewBundle/Model/ScoredReview.php

class ScoredReview extends RatedReview
{
}

Then I implement the entities by extending the models, like so:

// Project/ReviewBundle/Entity/Review.php

use Project\ReviewBundle\Model\Review as BaseReview;

class Review extends BaseReview
{
}

// Project/ReviewBundle/Entity/RatedReview.php

use Project\ReviewBundle\Model\RatedReview as BaseRatedReview;

class RatedReview extends BaseRatedReview
{
}

// Project/ReviewBundle/Entity/ScoredReview.php

use Project\ReviewBundle\Model\ScoredReview as BaseScoredReview;

class ScoredReview extends BaseScoredReview
{
}

So the inheritance is happening on the model side. Doctrine can't seem to see this, and maps them to separate tables. I understand this is because Doctrine only looks for entities extending other entities, not entities extending models.

Is there a better way for me to separate the models from the entities, while retaining the ability to extend entities? Is this where traits come in handy?

Put another way, is there anyway that I can have a tree made of models, and a tree made of entities that extends those models?

Answer 1

I've come up with a solution for this issue, and it does involve traits.

What I'm doing is basically trying to create several variations of a table. The relationship between the reviews is more horizontal than vertical (One type of review might have ratings, another one a video, another both). Traits are apparently perfect for horizontal relationships, so instead of creating models for each variation, I create traits.

So now my "models" look like this:

// Project/ReviewBundle/Entity/Review.php

use Project\ReviewBundle\Model\Review as BaseReview;

class Review extends BaseReview
{
}

// Project/ReviewBundle/Entity/RatedReviewTrait.php

trait RatedReviewTrait
{
}

// Project/ReviewBundle/Entity/ScoredReviewTrait.php

trait ScoredReviewTrait
{
}

And my entities look like this:

// Project/ReviewBundle/Entity/Review.php

use Project\ReviewBundle\Model\Review as BaseReview;

class Review extends BaseReview
{
}

// Project/ReviewBundle/Entity/RatedReview.php

use Project\ReviewBundle\Model\RatedReviewTrait;

class RatedReview extends Review
{
    use RatedReviewTrait;
}

// Project/ReviewBundle/Entity/ScoredReview.php

use Project\ReviewBundle\Model\RatedReviewTrait;
use Project\ReviewBundle\Model\ScoredReviewTrait;

class ScoredReview extends Review
{
    use RatedReviewTrait;
    use ScoredReviewTrait;
}

My models stay separated from my entities and as a bonus I decouple the variations from each other – pretty awesome. The only issue I see is that this requires PHP >= 5.4.