Value Injecter : Dto to Domain Model (NHibernate)

Question

I am using ValueInjecter to map properties from a Domain model to a DTO served up via a Service Layer. The service in question also accepts updates... so an updated DTO is passed in and this is then injected to the domain object and saved.

    // Domain
    public class Member 
    {
      public Country Country { get; set; }
    }

    public class Country 
    {
      public string Code { get; set; }
      public string Name { get; set; }
    }

    //Dto
    public class MemberDto 
    {
       public string CountryCode { get; set; }
    }

    //Transformation Method attempt 1
    public Member InjectFromDto (MemberDto dto, Member source)
    {
       source = source.InjectFrom<UnflatLoopValueInjection>(dto);
       return source;
    }

Now all this above code does is updates the Property Member.Country.Code which is obviously not what I need it to do.

So from the docs, I figured I needed to create an override and got this:

public class CountryLookup: UnflatLoopValueInjection<string, Country>
    {
        protected override Country SetValue(string sourcePropertyValue)
        {
            return countryService.LookupCode(sourcePropertyValue);
        }
    }


 //revised transformation call
 //Transformation Method attempt 2
    public Member InjectFromDto (MemberDto dto, Member source)
    {
       source = source.InjectFrom<UnflatLoopValueInjection>(dto)
                      .InjectFrom<CountryLookup>(dto);
       return source;
    }

My problem is during debugging, CountryLookup never gets called.

Possible reasons I can think of:

• Nhibernate Proxy classes causing value injecter to not match the Country type? Tho this doesnt make sense because it works during the flattening.
• Perhaps the unflattening isn't firing for some reason. I.e Dto is CountryCode and Domain is Country.Code

I need to use the CountryCode property on the Dto to call a countryService.LookupCode to return the correct object to use during the update injection.

Answer 1

Using the suggestion/reference from Omu this was the specific code to the problem.

 public class CountryLookup : ExactValueInjection
    {
        private ICountryService countryservice;

        public CountryLookup(ICountryService countryService)
        {
           this.countryService = countryService; 
        }

        protected override bool TypesMatch(Type s, Type t)
        {
            return (s == typeof(string)) && (t == typeof (Country));

        }
        protected override Object SetValue(object v)
        {
            if (v == null) 
                return null;

            var country = countryService.LookupCode((string) v);
            return country;
        }

        public override string SourceName()
        {
            return "CountryCode";
        }

        public override string TargetName()
        {
            return "Country";
        }    
    }

public Member InjectFromDto (MemberDto dto, Member source)
{
   source = source.InjectFrom<UnflatLoopValueInjection>(dto)
                  .InjectFrom<CountryLookup>(dto);
   return source;
}

Answer 2

unflattening would be to do this:

entity.Country.Code <- dto.CountryCode

what you need is:

entity.Country <- dto.CountryCode

so the solution for you would be to inherit an ExactValueInjection where you would go from CountryCode to Country.

what I recommend you to do is do the same that I did in the live demo of another project of mine http://awesome.codeplex.com

where I have something like this:

    public class Entity
    {
       public int Id{get;set;}
    }
    public class Member : Entity
    {
        public Country Country{get;set;}
    }
    public class MemberDto : DtoWithId
    {
        public int? Country {get;set;}
    }

and use these injections to go from entity to dto and back

    public class NullIntToEntity : LoopValueInjection
        {
            protected override bool TypesMatch(Type sourceType, Type targetType)
            {
                return sourceType == typeof(int?) && targetType.IsSubclassOf(typeof(Entity));
            }

            protected override object SetValue(object sourcePropertyValue)
            {
                if (sourcePropertyValue == null) return null;
                var id = ((int?) sourcePropertyValue).Value;

                dynamic repo = IoC.Resolve(typeof(IRepo<>).MakeGenericType(TargetPropType));

                return repo.Get(id);
            }
        }
//(you also need to have a generic repository, notice IRepo<>)    
    public class EntityToNullInt : LoopValueInjection
        {
            protected override bool TypesMatch(Type sourceType, Type targetType)
            {
                return sourceType.IsSubclassOf(typeof (Entity)) && targetType == typeof (int?); 
            }

            protected override object SetValue(object o)
            {
                if (o == null) return null;
                return (o as Entity).Id;
            }
        }

these injections will handle not just going from int? to Country and back but also any other type which inherits Entity

Answer 3

Is a framework calling the setter method? In most DI frameworks, the standard is lowercase 's' in the setMethod(). Just a first-thought recommendation.