CODEWITHSUNDEEP
nhibernatesingle-table-inheritance
Yoav
Yoav

Reputation: 2077

NHibernate - Single table per class hierarchy - inheriting classes are unknown

In my model all the derived classes have the same ** persistent** attributes and methods as the base abstract class. There are some class specific attributes which aren't persisted and methods have different implementation. Right now I have about 4 inheriting classes, and I will add more in the future. The nature of the application is that such classes may be added for different uses, so its impossible to know them in advance. The only given is that they will all share the same methods and persistent attributes. The is one column which will be used as discriminator.

I am struggling with strategy. Obviously I don't want to write a ClassMap for each derived class. In fact I's like the persistence layer to be completely ignorant of these derived classes. I am thinking of having the derived classes be able to be created off the base class and to return a base class.

I don't suppose I have any better option?

Upvotes: 1

Views: 463

Answers (1)

Diego Mijelshon
Diego Mijelshon

Reputation: 52735

Your approach is flawed in that the persistence layer can not be ignorant about the subclasses, because it needs to know what the class is when loading/storing.

What you can do is use a convention-based mapping instead of an explicit one (Fluent has Automapping, and ConfORM is convention/override based only), so you don't have to write every classmap.

In ConfORM, it's as easy as saying, for example, orm.TablePerClass<TheBaseClass>(), then mapper.CompileMappingFor(TheBaseClassAndAllItsSubclasses), and you'll get the mappings without any additional effort.

Upvotes: 2

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