I am using the Table Per Subclass strategy to persist an inheritance hierarchy:

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alt text http://dl.dropbox.com/u/1563210/budget%20obj%20graph.jpg

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I am running into some confusion as to how to map the Debit class, which implements 2 interfaces. I may be overthinking it; I'm still learning NH.

Thanks for any input.

EDIT

What's confusing me is that the only properties that my concrete classes have, the开发者_C百科y are getting from those interfaces. This is why I think I will have to map the Interfaces along with the concrete classes.

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NHibernate doesn't know or care about the interfaces. You can't, for example, use NHibernate to query for objects that implement a specific interface. You have a table-per-class mapping so you should map it with subclass declarations as described in the documentation.

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I'm very new to NHibernate myself but have done something similar so hopefully if I post something along the right lines It'll give us a start so you can comment and in the spirit of stackoverflow someone can edit my answer perhaps.

I think basically the hbm needs to use "subclass", "joined-subclass" or "union-subclass" to achieve what you're looking for.

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                   assembly="YourAssembly.Bll"
                   namespace="YourAssembly.Bll.Domain">
  <class name="Transaction" table="Transaction">
    <id name="Id">
      <generator class="native"/>
    </id>
    <property name="Amount" not-null="true" />
    <property name="Currency"/>

    <joined-subclass name="Debit" table="DebitTransaction">
      <key column="TransactionId"/>
      <property name="CardHolderName" not-null="true" />
    </joined-subclass>

  </class>
</hibernate-mapping>

The Hibernate docs on inheritance are very useful