Say I have an immutable ICompositeUserType to deal with a DateRange, or Money, and then it turns out that I have another value object (ie, immutable) that has either a DateRange or Money property value in it. For example, a Name that has an EffectivePeriod (DateRange).

The DataRangeUserType encapsulates some logic I wouldn't want duplicated.

Can I reuse my DataRangeUserType inside of a NameUserType? How?

Cheers,

Berryl

UPDATE

Below is the summary comment on ICompositeUserType taken from the NHibernate source code which suggests what I am thinking of can be done, just not sure how. Admittedly, the component strategy is easy and works great, until you think you might want to use the same compoent elsewhere

/// <summary>
/// A UserType that may be dereferenced in a query.
/// This interface allows a custom type to define "properties".
/// These need not necessarily correspond to physical .NET style properties.
///
/// A ICompositeUserType may be used in almost every way
/// that a component may be used. It may even contain many-to-one
/// associations.
///
/// ...
/// </summary>

Using component mapping

<component name="MyCompositeComponent" class="...">开发者_StackOverflow中文版;

  <property name="Name" not-null="true" length="50"/>

  <property name="Price" type="...MoneyUserType">
      <column name="Amount"/>
      <column name="Currency"/>
  </property> 

  <property name="EffectivePeriod" type="...DateRangeUserType">
      <column name="EffectiveStart"/>
      <column name="EffectiveEnd"/>
  </property> 

</component>    

Hibernate lets you compose value types in Components:

<class name="MyClass" table="MyTable" >
  ...
  <component name="_namedPeriod">

      <property name="_name" column="PeriodName" />

      <property name="_effectivePeriod" 
                type="MyNamespace.DataRangeUserType, MyAssembly" >

          <column name="PeriodStart" />
          <column name="PeriodEnd" />
      </property>

  </component>
  ...
</class>

Classes look like this:

// entity
public class MyClass {
    private NamedPeriod _namedPeriod;
}

// immutable value object
public class NamedPeriod {
    private readonly String _name;
    // immutable value object
    private readonly DateRange _effectivePeriod;
}

The idea that you use UserTypes for primitives like DateRange and Money and Component for a larger immutable value objects. Components can also include other components.