Where to put common business logic in DDD with MVC

Question

Providing I have the following scenario: I have a Web application where users can deposit money to their accounts (wire transfer). When a user deposits money to their account, they should click the "Refresh my balance" button to refresh their balance.

The business logic behind the "Refresh my balance" is the following:

1. Refresh balance, for example by calling a bank's webservice.
2. If there is new money, subtract a % from it as a fee.

The thing is that I would not like to allow refreshing balance without proceeding new deposit fees.

I have two services:

class AccountService
{
    //The following calls the bank webservice to get the new balance and updates the account entity
    public function refreshBalance(Account account);
}

class FeeService
{
    //The following checks if there are deposits, and if there are it subtract a fee
    public function proceedNewFees(Account account);
}

My MVC controller action is the following right now:

public function refreshBalanceAction()
{
    $account = $this->accountService->getAuthenticatedAccount();
    $this->accountService->refreshBalance($account);
    $this->accountService->proceedNewFees($account);
}

As you can see, in the controller I have some business logic. I would like to move it to the Domain layer. Where is the best place to put this business logic from the controller? Create a new CommonLogicService? Implement it in the AccountModel (and if so, how to refer to the AccountService instance being in the AccountModel? DI?)?

Answer 1

The way you describe it, I would put the code to update the balance in a separate UpdateBalanceService-class. Then create a new class 'RefreshBalanceService' that contains both the UpdateBalanceService and a ProcessNewFeesService. The UpdateBalanceService-class would then call both services and perform the necessary actions. It is then a matter of implementing your refresh-code so that it uses the UpdateBalanceService class to do its work, which will in turn delegate to the subservices to perform its tasks.