On Aug 29, 1:29 pm, Thomas Koch <[email protected]> wrote:
>
> How do you see/solve the "testability problem" that I was talking
> about?
>
I can see how injecting DAOs into your domain could make testing
problematic.
Also, as I've reflected upon the code I posted earlier in this thread,
I've come to hate it. :) I hate it because of the customer/order
relationship, though -- not because of the principle I was trying to
demonstrate. In other words, I still think it's okay to inject DAOs
into your domain model, but I agree it's probably less than ideal.
It's hard to talk about this stuff in the abstract. I like what you
said about the problem of DAOs having lots of methods and it not being
clear what's being used where. Creating fine-grained DAOs might help
to mitigate that pain (Interface Segregation Principle if you want a
label).
Brendan's example had to do with validation. He has Doctors, Patients,
Visits, and Services. A doctor can provide a certain set of services.
A patient can receive multiple services during one visit, and those
services may come from one or many doctors. If validation of these
configurations is non-trivial then I would consider having a
'Validator' or 'ValidationService' or something along those lines.
I'm having trouble envisioning the validation scenario, so I'll leave
that aside for now. But based on what Brendan has mentioned I would
think of something along these lines...
public interface IServiceDao
{
IList<Service> GetServicesByDoctor(int doctorId);
}
public interface IDoctorDao
{
IList<Doctor> GetDoctorsByService(int serviceId);
}
public class Doctor
{
private IServiceDao _serviceDao;
public IList<Service> GetServices()
{
return _serviceDao.GetServicesByDoctor(Id);
}
public int Id { get; set; }
}
public class Service
{
private IDoctorDao _doctorDao;
public IList<Doctor> GetOfferingDoctors()
{
return _doctorDao.GetDoctorsByService(Id);
}
protected int Id { get; set; }
}
public class Visit
{
public IList<Doctor> Doctors { get; set; }
public IList<Service> Services { get; set; }
public Patient Patient { get; set; }
}
public class Patient
{ }
--Stuart
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