how to clone objects ?

antares · **Posted:** Mon Mar 06, 2006 5:52 pm

Hi, im developing an Questions-Answers program, having Evaluations wich have multiple Questions and this last have multiple Answers... selecting an Evaluation i wanna do a kind of "Save As.." those save the Evaluation his Q & respective Answers like new objects, any idea how to do this?

Im using NHibernate 1.0 & SQL server 2000

Thanks!!

antares · **Posted:** Tue Mar 07, 2006 8:40 am

here´s the .hbm files for the upper level class

Code:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0">
   <class name="Business.Data.Evaluations,Business" table="Evaluations">

      <id name="IdEvaluation" column="idEvaluation" type="Int32" unsaved-value="0">
         <generator class="native"/>
      </id>
      <bag name="QuestionsList" inverse="true" lazy="true" >
         <key column="idEvaluation" />
         <one-to-many class="Business.Data.Questions,Business" />
      </bag>
      <property column="title" type="String" name="title" not-null="true" length="50" />
      <property column="tDisponible" type="Int32" name="TDisponible" />
      <property column="tAviso" type="Int32" name="TAviso" />
      <property column="puntaje" type="Int32" name="Puntaje" />
      
   </class>
</hibernate-mapping>

and the Questions mapping:

Code:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0">
   <class name="Business.Data.Questions,Business" table="Questions">

      <id name="IdQuestion" column="idQuestion" type="Int32" unsaved-value="0">
         <generator class="native"/>
      </id>
      <bag name="AnswersList" inverse="true" lazy="true" >
         <key column="idQuestion" />
         <one-to-many class="Business.Data.Answers,Business" />
      </bag>
      <many-to-one name="IdEvaluation" column="idEvaluation" class="Business.Data.Evaluations,Business" />
      <many-to-one name="IdCategoria" column="idCategoria" class="Business.Data.Categorias,Business" />
      <property column="nQuestion" type="String" name="NQuestion" not-null="true" length="255" />
      <property column="activa" type="Boolean" name="Activa" not-null="true" />
      
   </class>
</hibernate-mapping>

here's the mapping for the Answers

Code:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0">
   <class name="Business.Data.Answers,Business" table="Answers">

      <id name="IdAnswer" column="idAnswer" type="Int32" unsaved-value="0">
         <generator class="native"/>
      </id>
      <many-to-one name="IdQuestion" column="idQuestion" class="Business.Data.Questions,Business" />
      <property column="nAnswer" type="String" name="NAnswer" not-null="true" length="255" />
      <property column="valid" type="Boolean" name="Valid" not-null="true" />
      
   </class>
</hibernate-mapping>

i need to "Save as..." (clone except by the id) an upper lever class Evaluations and with this all the related Questions and all the Answers for these related questions.

Tks again!

paulh · **Posted:** Wed Mar 08, 2006 3:10 pm

Cloning is fundamentally a domain question, not a persistence one, since you may want to do a "shallow" (copy values but keep the same entity references) or "deep" (create new entities to refer to).

Implement Clone methods e.g. (CloneShallow, CloneDeep) on your low-level classes and then either have a factory class to do the appropriate level of cloning.

One you have your new top-level class, just call saving the normal manner and it will persist it. NB When you clone entities, make sure that you initialize any identity properties so that NHibernate can tell it's a new object.