casting an object as a interface via generic

[Dave Novo 51]

Hello,

I am using Delphi Seattle. I am wondering if something like this is possible. I cannot figure out how query if the object supports T at the base level.

 

TMyClass=class
public
  function MyFunc<T:Interface>:T;
end


TMyDescendent=class(TMyClass,ISomeInterface)
public
   function ReturnMyInt:ISomeInterface;
end;


function TMyDescendent.ReturnMyInt:ISomeInterface
begin
  result:=MyFunc<ISomeInterface>;
end


function TMyClass.MyFunc<T>:T
begin
   // do some stuff here
  Supports(self,T,result);// does not compile
  result:=self as T;// does not compile
end;

 

of course, I can always chane MyFunc to math the Supports signature (i.e. pass in IID and out Obj) but I was wondering if there was a way to do this with generics

Edited March 24, 2021 by Dave Novo

[Stefan Glienke 2002]

uses
  TypInfo;

function TMyClass.MyFunc<T>: T;
var
  p: PTypeData;
begin
  p := GetTypeData(TypeInfo(T));
  Assert(ifHasGuid in p.IntfFlags);
  Supports(Self, p.GUID, Result);
end;

 

[Dave Novo 51]

awesome. Thank you so much!