Fluent NHibernate inheritance mapping problem

Question

I am using Fluent NHibernate with table per subclass inheritance mapping. I want to reference to a list of specific objects, but i can't figure out, how to restict the result to objects of one specific class.



class PetMap : ClassMap<Pet>
{
    public PetMap()
    {
        Id(c => c.ID).GeneratedBy.Identity();            
    }
}

class DogMap : ClassMap<Dog>
{
    public DogMap()
    {
       Mac(c => c.DogSpecificProperty);                                
    }
}

class CatMap : SubclassMap<Cat>
{
    public CatMap()
    {
       Mac(c => c.CatSpecificProperty);                                    
    }
}

class PersonMap : ClassMap<Person>
{
    public PersonMap()
    {  
        Id(c => c.ID).GeneratedBy.Identity();

        //this works fine
        HasMany(c => c.Pets);

        //this dosen't work, because the result contains dogs and cats
        //how can I tell NHibernate to only fetch dogs or cats?
        HasMany<Pet>(c => c.Cats);
        HasMany<Pet>(c => c.Dogs);
    }
}

class Pet
{ 
   int ID;
}
class Dog : Pet
{
   object DogSpecificProperty;
}
class Cat : Pet
{
   object CatSpecificProperty;
}
class Person
{
   int ID;
   IList<Pet> Pets;
   IList<Dog> Dogs;
   IList<Cat> Cats;
}

Can anyone help me? Please excuse my poor english.

Joseph · Accepted Answer · 2009-11-12 18:04:25Z

1

I'm not an expert in Fluent NH, but it seems to me that your person map should look like this:

class PersonMap : ClassMap<Person>
{
    public PersonMap()
    {  
        Id(c => c.ID).GeneratedBy.Identity();

        //this works fine
        HasMany(c => c.Pets);

        //this dosen't work, because the result contains dogs and cats
        //how can I tell NHibernate to only fetch dogs or cats?
        HasMany<Cat>(c => c.Cats);
        HasMany<Dog>(c => c.Dogs);
    }
}

Because you're Person has a Dogs property which is an IList not IList, and conversely the same for Cats.

answered Nov 12, 2009 at 18:04

Joseph

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2 Comments

trichterwolke Over a year ago

<code> HasMany<Pet>(c => c.Cats) </code> This look a litle bit stupid, but i think it is correct, because the Pet table has a reference to the Person table. I get this solution from an other stack overflow question. It seems to me, that HasMany<Pet>(c => c.Cat) does the same as HasMany<Cat>(c => c.Cat).KeyColumn("PetID"). In both cases i get a result of cats and dogs.

Joseph Over a year ago

@trichterwolke if you're saying that the Cat and Dog classes are actually coming from the Pet table in your DB, then I would think that you would say that in the CatMap and DogMap, not in the PersonMap. I believe that's how I did that in the past when using FNH.

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