I have modeled my application using multiple 'user' domain objects.

  • Candidate
  • Recruiter
  • Administrator

Each entity extends from an AbstractUser implementing UserInterface.

interface UserInterface
    public function getEmail();
    public function setEmail($email);
    public function getPassword();
    public function setPassword($password);

They all have their own a services CandidateService, AdminService etc implementing UserServiceInterface

interface UserServiceInterface
   public function getUserByEmail();

My problem arises when I need to fetch a user by their email address (say PasswordResetService) I am unable to determine which service I should be calling as the email could be either of them. I am also using mongoDB so I cannot simply run a native query joining the 'tables'.

My current thought is that I have to inject each service into the PasswordResetService and call getUserByEmail() on each of them until I get my desired user.

class PasswordResetService
   public function getUserByEmail($email) 
       $user = $this->userService->getUserByEmail($email);
       if ($user) return $user;

       $user = $this->recruiterService->getUserByEmail($email);
       if ($user) return $user;

       // etc ...

From a design perspective the above seems to me like a poor approach as should I add a new user 'type' I would need to update the password service also.

Is there a better way of achieving this?

  • Do the services need to have different names? Nov 21, 2014 at 12:09
  • @JamesMcLeod I assume you mean within the context of PasswordResetService? So rather than $this->userService perhaps an array of user services? If this is what you mean, then no, they don't need different names as I would only ever be calling methods that are within the UserServiceInterface.
    – AlexP
    Nov 21, 2014 at 12:37
  • 1
    If the invoking functionality needs to be able to distinguish between the three types of actor, than you need to provide a mechanism allowing it. If it does not need to know (because you could call getUserByEmail directly for each, and similarly for every other service invoked), then you don't. I don't think there are any other good design choices. Nov 21, 2014 at 12:44

1 Answer 1


I would approach this by having a top level UserService that doesn't care what type of user it's dealing with.

If it gets a request for a user by email, it can look up on the database which type of user is correct and delegate the request to the correct service. This may sound a little inefficient, but used with an appropriate query caching later it's actually fine.

Other methods that are passed a user object could perhaps use double dispatch to forward the request to the correct service object., thus eliminating the need to hit the database for these operations.

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