Generics and JSON serialisation in Delphi XE5 reflection - json

Question

I'm trying to serialise/deserialise the TMySerializableClass declared in the below unit:
unit Unit6;
interface
uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Generics.Collections, System.SyncObjs, DBXJSon,
DBXJSonReflect;
type
TForm6 = class(TForm)
Button1: TButton;
Memo1: TMemo;
procedure Button1Click(Sender: TObject);
private
public
{ Public declarations }
end;
TMySerializableClass<T> = class
MyStringField: string;
MyIntegerField: Integer;
MyBooleanField: Boolean;
end;
var
Form6: TForm6;
implementation
{$R *.dfm}
procedure TForm6.Button1Click(Sender: TObject);
var
Mar: TJSONMarshal; //Serializer
UnMar: TJSONUnMarshal; //UnSerializer
SerializedObject: TJSONObject;
aMySerializableClass1: TMySerializableClass<Integer>;
aMySerializableClass2: TMySerializableClass<Integer>;
aString: string;
begin
try
aMySerializableClass1:= TMySerializableClass<Integer>.Create;
aMySerializableClass2:= TMySerializableClass<Integer>.Create;
Mar:= TJSONMarshal.Create(TJSONConverter.Create);
try
SerializedObject := Mar.Marshal(aMySerializableClass1) as TJSONObject;
finally
Mar.Free;
end;
Memo1.Text:= SerializedObject.ToString;
// UnMarshalling Kid
UnMar := TJSONUnMarshal.Create;
try
aMySerializableClass2 := UnMar.UnMarshal(SerializedObject) as TMySerializableClass<Integer>;
finally
UnMar.Free;
end;
finally
aMySerializableClass1.Free;
aMySerializableClass2.Free;
end;
end;
end.
When I serialise it everything works fine, while when deserialise to a new instantiated variable of the same kind I got the following error:
First chance exception at $74E5C41F. Exception class EConversionError with message 'Internal: Cannot instantiate type Unit6.TMySerializableClass<System.Integer>'. Process Project7.exe (2252)
Edit: this has something to do with the TMySerializableClass<T>, which
is a generic. If I declare it as TMySerializableClass the
deserialisation works fine.
Ideas?

Answer 1

Cannot test on XE5 but on Berlin 10.1 it worked for me after I added alias for instance of generic type as
TMySerializableClassInteger = TMySerializableClass<Integer>;
looks like Delphi does not generate RTTI information if you don't do it.
UPDATE. Seems Delphi does not need alias but just have some declaration of specialized class in interface part of the unit. So if you declare variable or form field as TMySerializableClass<Integer> it will also work.