Question

Hi I’m struggling do refine/refactoring a domain model and trying to move logic from application services into my domain model. Now I’m stuck with a NHibernate issue.

The model is a WorkEvaluation class that contains a Questionaire Template with Questions and it also contains a collection of QuestionWeight classes. The thing is that WorkEvaluation class also has an important property HitInterval that belongs closed to the QuestionWeight collection in WorkEvaluation. The concept is that you conduct an evaluation by answering a lot of questions (the anserws are excluded in this example) and finaly you apply some weights (percent weights) that modify answer scores. That means you can make some questions more important and other less important. Hit interval is also a tuning parameter that you use when you calculate TOTAL WorkEvaluation score (including weight modifications) and the result is for example: Totalscore = 100, Hitinterval 5% than we get a totalinterval of 95-105 and can be used to match other evaluations.

Enough of background.
I Want to encapsulate both list of QuestionWeights and HitInterval in a Value Object QuestionScoreTuning since these belongs together and should be applied at the same time.
And I also want to add some business logic into QuestionScoreTuning that do not belongs to workEvaluation.
How do I map i Fluent Nhibernate a Value Object (Component) that has the one-to-many collection and HitInterval and the reference back? This is my current code:

public class WorkEvaluation : DomainBase<long>, IAggregateRoot
{
 public void ApplyTuning(QuestionScoreTuning tuning)
        {
            QuestionScoreTuning = tuning;
            //TODO Raise Domain Event WorkEvaluationCompleted - 
            // which should recalculate all group scores
        }
 public QuestionScoreTuning QuestionScoreTuning { get; protected set; }
}

public class QuestionScoreTuning : ValueObject
    {
        private IList<QuestionWeight> _questionWeights;

        public QuestionScoreTuning(IList<QuestionWeight> listOfWeights, long hitInterval)
        {
            _questionWeights = listOfWeights;
            HitInterval = hitInterval;
        }

        public long HitInterval { get; protected set; }

        protected override IEnumerable<object> GetAtomicValues()
        {
            return _questionWeights.Cast<object>();
        }

        /// <summary>
        /// A list of all added QuestionWeights for this WorkEvaluation
        /// </summary>
        public IList<QuestionWeight> QuestionWeights
        {
            get { return new List<QuestionWeight>(_questionWeights); }
            protected set { _questionWeights = value; }
        }

        protected QuestionScoreTuning()
        {}
    }

public class QuestionWeight : DomainBase<long>, IAggregateRoot
{
    public QuestionWeight(Question question, WorkEvaluation evaluation)
    {
        Question = question;
        WorkEvaluation = evaluation;
    }

    public Weight Weight { get; set; }
    public Question Question { get; protected set; }
    public WorkEvaluation WorkEvaluation { get; protected set; }

    public override int GetHashCode()
    {
        return (Question.GetHashCode() + "|" + Weight).GetHashCode();
    }

    protected QuestionWeight()
    {}
}

Fluent Mappings:

public class WorkEvaluationMapping : ClassMap<WorkEvaluation>
    {
        public WorkEvaluationMapping()
        {
            Id(x => x.ID).GeneratedBy.Identity();
            References(x => x.SalaryReview).Not.Nullable();
            References(x => x.WorkEvaluationTemplate).Column("WorkEvaluationTemplate_Id").Not.Nullable();
            Component(x => x.QuestionScoreTuning, m =>
                                                      {
                                                          m.Map(x => x.HitInterval, "HitInterval");
                                                          m.HasMany(x => x.QuestionWeights).KeyColumn("WorkEvaluation_id").Cascade.All();
                                                      });

            }
    }

public class QuestionWeightMapping : ClassMap<QuestionWeight>
    {
        public QuestionWeightMapping()
        {
            Not.LazyLoad();
            Id(x => x.ID).GeneratedBy.Identity();
            Component(x => x.Weight, m =>
                                         {
                                             m.Map(x => x.Value, "WeightValue");
                                             m.Map(x => x.TypeOfWeight, "WeightType");
                                         });
            References(x => x.Question).Column("Question_id").Not.Nullable().UniqueKey(
                "One_Weight_Per_Question_And_WorkEvaluation");
            References(x => x.WorkEvaluation).Column("WorkEvaluation_id").Not.Nullable().UniqueKey(
                "One_Weight_Per_Question_And_WorkEvaluation");
        }
    }

All I want to accomplish is to move collection of QuestionWeights and HitInterval into a Value Object (Component mapping) since these will still be inside db table WorkEvaluation.

P.S I’ve look at some example solution DDDSample.net (Eric Evans DDD example in c#) and they accomplished this with the Itinerary class that takes a list as ctor parameter and is mapped as a Cargo component. Difference is that example has a list of valueobjects Leg BUT Leg has references to Location which is an entity class.

Hopefully maybe someone knows how to accomplish this. Thanks in advance…
/Bacce

Answer 1

Well. I Finally solved it. Now my WorkEvaluation object can be Applied with a QuestionScoreTuning object (a valueobject) that contains the list of weight and hitinterval. This turns out great and if anyone want more info about having collections inside value objects and mapping them in fluent NH, please ask here with a comment. I can supply code examples…