Symfony 3 fluid entity relations - symfony

Question

I am trying to implement a time tracking mechanism in my custom project management app.
This app contains multiple entities (tickets, projects, wiki pages, sprints, ...)
I want my timetracking to be "generic" in the sense that I want users to be able to log time against a ticket, project, wiki page, ...well any entity actually.
Now, I am trying to figure out what database schema (relation) to use for my TimeLog entity.
I could theoretically create a relation to each entity I have in my app, but that will require me to keep updating schema when I introduce new entities later on.
Has anybody every implemented anything like this?
All suggestions are welcomed.
Many thanks in advance.

Answer 1

I faced a similar situation in my app while trying to add comments, likes and other types of elements whose behaviour would not really depend on the entity they are attached to.
The solution I eventually chose was to have two fields in my referring entities (e.g. Comment) to hold both the id of the entity being referred to and its type. Since I was using this multiple times, I put the properties into the following trait:
namespace AppBundle\Entity\Traits;
use Doctrine\ORM\Mapping as ORM;
trait EntityReferenceTrait
{
/**
* #ORM\Column(name="reference_id", type="integer")
*/
private $referenceId;
/**
* #ORM\Column(name="reference_type", type="integer")
*/
private $referenceType;
/* ... setters & getters ... */
}
Then I could use it in the entities holding those kind of references:
/**
* #ORM\Table(name="comments", indexes={#ORM\Index(name="references", columns={"reference_id", "reference_type"})})
* #ORM\Entity(repositoryClass="AppBundle\Repository\Comment\CommentRepository")
*/
class Comment
{
/* ... other traits ... */
use \AppBundle\Entity\Traits\EntityReferenceTrait;
/* ... other fields & methods ... */
}
Note: I added an index for the references but it is not necessary for the whole thing to work properly. If you use such an index, beware of the order of your WHERE clauses if you want to benefit from it
In order to improve performance a bit and add additional configurations depending on the type of the entity being referred to, I handled settings directly in the config of my app. Thus, I have something like:
commentables:
news:
classname: AppBundle\Entity\News\News
type_id: 1
browse_route: news_comments
multiple_locales: false
...
This allows me to know precisely what kind of entities my Comment entity can refer. It also allows me to automatically hook specific listeners to the entities being referred to so that the removal of a referred entity triggers the removal of the related comments for example. I do this by processing the configuration in AppBundle/DependencyInjection/AppExtension.php (more about this here) and saving the needed listeners list into a parameter. Then, by adding a listener to the loadClassMetadata event, I can effectively handle the removal of related entities for example.
Here is the listener that hooks the listeners for specific lifecycle events of referred entities by using addEntityListener on the ClassMetadata instance:
namespace AppBundle\Listener;
use Doctrine\ORM\Event\LoadClassMetadataEventArgs;
class MappingListener
{
private $entityListenersMapping = [];
/**
* #param array $mappingConfig Associative array with keys being listeners classnames and values being arrays associating an event to a method name
*/
public function __construct(array $mappingConfig)
{
$this->entityListenersMapping = $mappingConfig;
}
public function loadClassMetadata(LoadClassMetadataEventArgs $eventArgs)
{
$classMetadata = $eventArgs->getClassMetadata();
if(!array_key_exists($classMetadata->name, $this->entityListenersMapping))
{
return;
}
// Hook the entity listeners in the class metadata
foreach($this->entityListenersMapping[$classMetadata->name] as $listenerClassName => $eventsCallbacks)
{
foreach($eventsCallbacks as $event => $methodName)
{
$classMetadata->addEntityListener($event, $listenerClassName, $methodName);
}
}
}
}
Either way, for this part, it mainly depends on the specific needs of your entity but I guess it is quite a common need that these "soft" foreign keys emulate a ON DELETE CASCADE behaviour via preRemove and postRemove events.
Considering the handling of those references and the entities owning them, I also created a EntityRefererManagerTrait to easily create services that manage those entities so that the other components interacting with them would not have to worry about the underlying configuration.
The interface of most public methods of those managers thus usually require:
the classname of the entity being referred to
the numeric id of the entity being referred to
With those two info and the configuration retrieved in my manager service, I can easily interact with the database even if, in my case, it stores an integer defined in the configuration as the reference type in place of the classname of the entity being referred to.
Based on this, I can enable comments, likes, votes, subscriptions and so on for any of my app entities (as long as its primary key is a single integer) with just a few more lines in my configuration files. No need to update database schema and with proper lifecycle events listeners being hooked, no worries about orphan entries in the database.
On a side note, it should be mentioned that you won't be able to retrieve referring entities from the inverse side as it won't be a real association. You won't benefit from foreign keys behaviours either. Thus, even if you emulate the ON DELETE CASCADE behaviour by listening to remove events, you won't be able to ensure that there are no orphans in your database if some DELETE operations are performed directly via DQL for example.