How to inject "unknown/dynamic" dependencies - php

Question

I have the following Notification entity:
As you can see, there is a field called "objectId" where I want to store the related object id depending on the notification type. Then I add the notification to an email queue. When the queue gets processed I have a problem to fetch the object from the specific service class. For example:
Notification Type 1: UserService::getUser($objectId)
Notification Type 2: CompanyService::getCompany($objectId)
So how could I define that relations without having troubles to add more and more notification types. It feels bad to inject all the needed services and handle it through thousands of "if this than that" :)

Answer 1

If you injected the object instead of the id, you wouldn't need to call an additional service inside the notification to get the appropriate instance.
If the Notification doesn't need to know about what kind of object its using, just depend on an interface that both User and Company implement, and inject those objects directly into Notification.
E.g.:
interface EmailNotifiableEntity {
function getLabel()
function getEmailAddress()
}
class User implements EmailNotifiableEntity {
public function getLabel() {
return $this->getName() . " " . $this->getFullName();
}
public function getEmailAddress() {
return this->getEmailAddress();
}
}
class Company implements EmailNotifiableEntity {
public function getLabel() {
return $this->getCompanyName();
}
public function getEmailAddress() {
return this->getNotificationsEmail();
}
}
class Notification {
public function __construct(EmailNotifiableEntity $entity) {
$this->entity = $entity;
}
public function send() {
$address = $entity->getEmailAddress();
$label = $entity->getLabel();
// do your thing to send your notification
}
(Implementation is a bit bare-bones, so take what you need and build upon it). This way, when you instantiate your Notification you inject the depended upon entity without knowing its specific kind.