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AutoMapper - object to object mapper

Acest mic framework ne ajuta cand trebuie sa mapam doua entita cu aceleasi propietati. In mod traditional pentru a face acest lucru trebuie sa scriem ceva de genul:
CarDb carDb = LoadFromDb(id);
// ...
Car car = new Car()
Type = carDb.Type,
Number = carDb.Number,
Owner = varDb.Owner,
RegFrom = carDb.RegFrom
Acest caz apare mai ales cand avem o aplicatie pe mai multe nivele, iar modelul care persista in baza de baza de date si modelul care ajunge la client sunt diferite.
Ce poate sa faca AutoMapper, este sa faca automat copierea valorilor proprietarilor, fara sa mai scrim noi cod. In cazul in care propietatea primeste o alta valorea sau are un nume diferit, putem sa scriem o expresie lambda care sa faca conversia.
Mai jos o sa gasiti cateva exenple:
1. Mapare intre doua entitati Car si CarDb
// Creare mapare.
Mapper.CreateMap<CarDb,Car>() ;
// Conversia propriu-zisa.
Car car = Mapper.Map<CarDb,Car>(carDb) ;
In loc sa avem o lista de propietati la care sa facem atribuiire, a fost nevoie sa apelam doar metoda CreateMap.
2. Maparea a doua propietati de tipuri diferite.
Sa presupunem ca Car contine o propietate IsHit de tip bool, iar CarDb contine aceiasi propietate, dar este de tipul int.
Pentru acest lucru este nevoie sa cream un nou ValueResolver care sa stie sa converteasc─â din int in bool. ValueResolver este un tip de data definit de AutoMapper, folosit pentru a face conversii intre date.
public class HitIntToBoolResolver : ValueResolver<int,bool>
protected ovveride bool ResolveCore(int val)
return val==1;
Iar pentru a face maparea trebuie pe CreateMap sa adaug─âm resolver-ul custom:
car => car.IsHit,
x => x.ResolveUsing<HitIntToBoolResolver>().FromMember( m => m.IsHit));
In acest moment, pentru propietatea IsHit, se va face o conversie automata din int in bool.
3. Cum sa atribuim o valoare custom la o propietate.
Sa presunem ca entitatea Car are o propietate FullNumber de tip string formata din RegDate+Number. Pentru a putea seta aceasta valoare in AutoMapper este nevoie sa scriem urmatorul cod:
car => car.FullNumber,
x => x.MapFrom( e => e.RegDate.ToString() + e.Number ));
In acest fel putem genera valori custom orice propietati.
4. In cazul in care entitatea are propietati care la randul lor trebuie mapate, ajunge sa definim maparea tuturor tipurilor de date implicate, in ncazul nostru este nevoie sa definim o mapare in plus pentru tipul de data Builder( presupunem ca entitatea Car are o propietare cu numele BuildBy de tip Buildder.
AutoMapper va detecta automat ca aceasta propietate este deja mapata si va folostii maparea definita deja.
Mapper .CreateMap<CarDb,Car>();
Car car = Mapper.Map<CarDb,Car>(carDb) ;

Din punct de vedere a vitezei, nu va asteptati sa fie la fel de rapid. In spate AutoMapper se bazeaza pe Reflection. Fata de o mapare manuala este undeva de 6-7 ori mai lent. In cazul in care nu aveti nevoie de mii de conversii pe secunta, cred ca AutoMapper este o solutie foarte buna. Obtinem un cod mai usor de intretinut si mult mai clar.


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