I have a problem after updating to version 4 with inheritance. I have the following code:
public abstract class CarDA
{
}
public class StationCarDA : CarDA
{
}
public abstract class CarBL
{
public CarBL(string type)
{
}
}
public class StationCarBL : CarBL
{
public StationCarBL() : base("stationcar") {}
}
Mapper.CreateMap<CarDA, CarBL>()
.Include<StationCarDA, StationCarBL>();
Mapper.CreateMap<StationCarDA, StationCarBL>();
var dataAccessObject = new StationCarDA();
var result = Mapper.Map<CarDA, CarBL>(dataAccessObject);
Try it on dotnetfiddle: https://dotnetfiddle.net/p3JeNO
This worked in previous versions so that the result was a StationCarBL instance. Now I get the following error:
Mapping types:
CarDA -> CarBL
Test.CarDA -> Test.CarBL
Destination path:
CarBL
Source value:
Test.StationCarDA
Stack Trace:
[System.ArgumentException: Type needs to have a constructor with 0 args or only optional args
Parameter name: type]
[AutoMapper.AutoMapperMappingException:
Mapping types:
CarDA -> CarBL
Test.CarDA -> Test.CarBL
Destination path:
CarBL
Source value:
Test.StationCarDA]
That message does not make sense to me. I have defined the CarDA -> CarBL mapping and why is it trying to map to CarBL which is abstract?
Looks like its a bug in Automapper
https://github.com/AutoMapper/AutoMapper/issues/819
Related
iam trying to map just a long field coming from my url route to create a Query Object from my controller, can i use auto mapper
CreateMap(MemberList.None);
Source :-long id
Destination:-
public class GetPlanQuery : IRequest<PlanDto>
{
public long Id { get; }
public GetPlanQuery(long id)
{
Id = id;
}
internal sealed class GetPlanQueryHandler : IRequestHandler<GetPlanQuery, PlanDto>
{
//Logic will go here
}
}
Map i am using is as below
CreateMap<long, GetPlanQuery>(MemberList.None);
i am getting an exception while executing as
System.ArgumentException:
needs to have a constructor with 0 args or only optional args.'
As Lucian correctly suggested you can achieve this kind of custom mapping by implementing ITypeConverter:
public class LongToGetPlanQueryTypeConverter : ITypeConverter<long, GetPlanQuery>
{
public GetPlanQuery Convert(long source, GetPlanQuery destination, ResolutionContext context)
{
return new GetPlanQuery(source);
}
}
then specify it's usage in AutoMapper configuration:
configuration.CreateMap<long, GetPlanQuery>()
.ConvertUsing<LongToGetPlanQueryTypeConverter>();
EDIT
Alternatively, you can just use a Func:
configuration.CreateMap<long, GetPlanQuery>()
.ConvertUsing(id => new GetPlanQuery(id));
I have taken the MixedType example code that comes with the java stream client (https://github.com/GetStream/stream-java) and added a update step using updateActivities. After the update the activity stored in stream loses the 'type' attribute. Jackson uses this attribute when you get the activities again and it is deserialising them.
So I get:
Exception in thread "main" Disconnected from the target VM, address: '127.0.0.1:60016', transport: 'socket'
com.fasterxml.jackson.databind.JsonMappingException: Could not resolve type id 'null' into a subtype of [simple type, class io.getstream.client.apache.example.mixtype.MixedType$Match]
at [Source: org.apache.http.client.entity.LazyDecompressingInputStream#29ad44e3; line: 1, column: 619] (through reference chain: io.getstream.client.model.beans.StreamResponse["results"]->java.util.ArrayList[1])
at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:148)
at com.fasterxml.jackson.databind.DeserializationContext.unknownTypeException(DeserializationContext.java:849)
See here where I have updated the example:
https://github.com/puntaa/stream-java/blob/master/stream-repo-apache/src/test/java/io/getstream/client/apache/example/mixtype/MixedType.java
Any idea what is going on here?
The issue here is originated by Jackson which cannot get the actual instance type of an object inside the collection due to the Java type erasure, if you want to know more about it please read this issue: https://github.com/FasterXML/jackson-databind/issues/336 (which also provides some possible workarounds).
The easiest way to solve it, would be to manually force the value of the property type from within the subclass as shown in the example below:
#JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type", visible = true)
#JsonSubTypes({
#JsonSubTypes.Type(value = VolleyballMatch.class, name = "volley"),
#JsonSubTypes.Type(value = FootballMatch.class, name = "football")
})
static abstract class Match extends BaseActivity {
private String type;
public String getType() {
return type;
}
}
static class VolleyballMatch extends Match {
private int nrOfServed;
private int nrOfBlocked;
public VolleyballMatch() {
super.type = "volley";
}
public int getNrOfServed() {
return nrOfServed;
}
public void setNrOfServed(int nrOfServed) {
this.nrOfServed = nrOfServed;
}
public void setNrOfBlocked(int nrOfBlocked) {
this.nrOfBlocked = nrOfBlocked;
}
public int getNrOfBlocked() {
return nrOfBlocked;
}
}
static class FootballMatch extends Match {
private int nrOfPenalty;
private int nrOfScore;
public FootballMatch() {
super.type = "football";
}
public int getNrOfPenalty() {
return nrOfPenalty;
}
public void setNrOfPenalty(int nrOfPenalty) {
this.nrOfPenalty = nrOfPenalty;
}
public int getNrOfScore() {
return nrOfScore;
}
public void setNrOfScore(int nrOfScore) {
this.nrOfScore = nrOfScore;
}
}
I have a generic interface, and a class implementing that interface with a concrete type parameter. I also have a generic class using the generic interface as its type constraint, but the type parameter is restricted to be a subclass of a certain base class. I want to instance the generic class with the class implementing that interface but have a problem of converting the class to that interface. The following code illustrates all the classes I mentioned:
The base class:
class DomainBase
{
}
The class used as the type parameter in the interface
class Person : DomainBase
{
}
The generic interface:
public interface IRepository<T> where T : class
{
IEnumerable<T> Fetch();
T Persist(T item);
}
The class implementing the generic interface:
class PersonRepository : IRepository<Person>
{
public IEnumerable<Person> Fetch()
{
...
}
public Person Persist(Person item)
{
...
}
}
The generic class using the generic interface:
class DomainBaseViewModel<Repository>
where Repository : IRepository<DomainBase>, new()
{
private Repository repository = new Repository();
private ObservableCollection<DomainBase> items;
}
However, the following line can't get compiled because PersonRepository is unable to be converted to IRepository<DomainBase>:
var viewModel = new DomainBaseViewModel<PersonRepository>();
Although I can solve this issue by covariance but it disallows the use of the type parameter in parameter lists:
public interface IRepository<out T> where T : class
{
...
T Persist(object item);
}
class PersonRepository : IRepository<Person>
{
public Person Persist(object item)
{
...
}
}
So I have to convert the parameter to Person, which compromises type safety.
Is there a better way to allow covariance and the use of type parameter in parameter lists in this case?
No - the whole point of the restriction on covariance is that it guarantees safety. A PersonRepository isn't an IRepository<DomainBase> because you can't ask it to persist any arbitrary DomainBase object. What would you expect this code to do?
class Product : DomainBase {}
...
IRepository<DomainBase> repository = new PersonRepository();
repository.Persist(new Product());
PersonRepository doesn't know how to persist Product values.
If in some cases you only need the "read" parts of the repository interface, you could always call that out explicitly:
public interface IRepositoryReader<out T>
{
IEnumerable<T> Fetch();
}
public interface IRepository<T> : IRepositoryReader<T>
{
T Persist(T item);
}
Then your DomainBaseViewModel class could be:
class DomainBaseViewModel<TRepository>
where TRepository : IRepositoryReader<DomainBase>, new()
{
private TRepository repository = new TRepository();
private ObservableCollection<DomainBase> items;
}
That doesn't work if you want your DomainBaseViewModel to persist items as well though. In that case, perhaps it should be generic in the type of model as well:
class DomainBaseViewModel<TRepository, TEntity>
where TRepository : IRepository<TEntity>, new()
{
private TRepository repository = new Repository();
private ObservableCollection<TEntity> items;
}
Then:
var viewModel = new DomainBaseViewModel<PersonRepository, Person>();
I have a simple example that seems like it should work:
import CoreData
#objc protocol CoreDataModel {
#optional class func entityName() -> String
}
class AbstractModel: NSManagedObject, CoreDataModel {
class func create<T : CoreDataModel>(context:NSManagedObjectContext) -> T {
var name = T.entityName?()
var object = NSEntityDescription.insertNewObjectForEntityForName(name, inManagedObjectContext: context) as T
return object
}
}
So we have a class called AbstractModel which conforms to the protocol CoreDataModel, and CoreDataModel defines an optional class method called entityName.
However, this line:
var name = T.entityName?()
causes the error:
Expected member name or constructor call after type name
Any idea what I'm doing wrong?
Edit
Removing the word #optional from the declaration and changing the function a bit allows the code to compile, but now I get a runtime error saying that the
'Swift dynamic cast failed'
#objc protocol CoreDataModel {
class func entityName() -> String
}
class AbstractModel: NSManagedObject, CoreDataModel {
class func entityName() -> String {
return "AbstractModel"
}
class func create<T : CoreDataModel>(aClass:T.Type, context:NSManagedObjectContext) -> T {
var name = aClass.entityName()
var object = NSEntityDescription.insertNewObjectForEntityForName(name, inManagedObjectContext: context) as T
return object
}
}
I cannot explain why your code causes a runtime exception. But it works if you change
the function prototype
class func create<T : CoreDataModel>(aClass:T.Type, context:NSManagedObjectContext) -> T
to
class func create<T : NSManagedObject where T: CoreDataModel>(aClass:T.Type, context:NSManagedObjectContext) -> T
Assuming that your managed object subclass conforms to the protocol, for example
extension Event : CoreDataModel {
class func entityName() -> String {
return "Event"
}
}
then this works and creates a new object:
let newManagedObject = AbstractModel.create(Event.self, context: context)
Alternatively, you could use the approach from the answer to
"Swift: return Array of type self" and
define an extension to the NSManagedObjectContext class:
extension NSManagedObjectContext {
func create<T : NSManagedObject where T : CoreDataModel >(entity: T.Type) -> T {
var classname = entity.entityName()
var object = NSEntityDescription.insertNewObjectForEntityForName(classname, inManagedObjectContext: self) as T
return object
}
}
Then a new object would be created as
let newManagedObject = context.create(Event.self)
From "The Swift Programming Language"
Because T is a placeholder, Swift does not look for an actual type called T.
As T is not a real type, it is maybe not useful to cast to T.
I have a Person and a PersonViewModel. I created a map from Person => PersonViewModel. The problem is that PersonViewModel's only constructor needs an argument (it has a dependency that I want to be injected) and AutoMapper is complaining because it says it needs a parameterless constructor.
To fix it, I used the ConstructServicesUsing method, but I haven't been successful with it :(
To illustrate the case, I created a test for you to see what I'm doing. It's pretty simple:
[TestMethod]
public void TestConstructServicesUsing()
{
Mapper.Initialize(configuration =>
{
configuration.ConstructServicesUsing(FactoryMethod);
configuration.CreateMap<Person, PersonViewModel>();
});
Mapper.AssertConfigurationIsValid();
var person = new Person();
var personViewModel = Mapper.Map<Person, PersonViewModel>(person);
}
private object FactoryMethod(Type type)
{
throw new NotImplementedException();
}
}
The rest of the code is the classes and interface definitions. They are almost empty.
public class SomeyDependency : ISomeDependency
{
}
public class PersonViewModel
{
private readonly ISomeDependency service;
public PersonViewModel(ISomeDependency service)
{
this.service = service;
}
public string Name { get; set; }
}
public class Person
{
public string Name { get; set; }
}
public interface ISomeDependency
{
}
As you see, I provide AutoMapper with a FactoryMethod, but it never get called.
When it reaches the last line of the test (Mapper.Map<...>()) it throws an excepton saying:
AutoMapper.AutoMapperMappingException:
Mapping types:
Person -> PersonViewModel
MappingWithContainerTests.Person -> MappingWithContainerTests.PersonViewModel
Destination path:
PersonViewModel
Source value:
MappingWithContainerTests.Person ---> System.ArgumentException: Type needs to have a constructor with 0 args or only optional args
Parameter name: type
What's the problem?
Why isn't the FactoryMethod being called?
As #khorvat mention where is missing .ConstructUsingServiceLocator(), for concrete mapping.
Also you can set constructor directly by
.ConstructUsing(source => Method(source.anySourceOptions))
Or as exception said:
PersonViewModel, must have a constructor with 0 args or only optional
args. You have only one constructor with 1 not optional argument
you may create one more constructor without args:
public PersonViewModel()
{
this.service = new SomeDependency();
}
I'm using .NET Core 3.1 and Automapper.Extensions.Microsoft.DependencyInjection.
This does not work for me (Same error as yours):
public class AutoMapping : Profile
{
public AutoMapping()
{
CreateMap<Context, MainViewModel>()
.ReverseMap()
.ConstructUsingServiceLocator();
}
}
But this does work:
public class AutoMapping : Profile
{
public AutoMapping()
{
CreateMap<Context, MainViewModel>()
.ConstructUsingServiceLocator()
.ReverseMap();
}
}
I still do not fully understand the cause.