Question

I am using NHibernate with a NullObject pattern to make my views simpler.
I use a solution found here by James Gregory

public Address GetAddressOrDefault()
{
  return Address ?? new NullAddress();
}

And Person has an Address property and so on….

This is working very good until I try to save my Person object for a person without an address. Since I created a new instance of the NullPerson object, NHibernate will try to save it. And gives me this:

ids for this class must be manually assigned before calling save():

Is there any way I can get NHibernate to not try to save my NullObjects? Or is there any other way I should be attacking this?

Answer 1

I know you’ve probably considered this but simplest solution seems to be to the reverse of

public Address GetAddressOrDefault()
{
  return Address ?? new NullAddress();
}

ie, prior to your save call:

public Address GetAddressOrNull(Address address)
{
  return address is NullAddress ? null : address;
}

Or…You might consider using a dedicated class for your ViewModel if things get more complex and using AutoMapper to do the monkey work.