从 TListT 下降使其具体化

Created: November-22, 2018

type
  TIntegerList = class(TList<Integer>)
  public
    function Sum: Integer;
  end;

...

function TIntegerList.Sum: Integer;
var
  Item: Integer;
begin
  Result := 0;
  for Item in Self do
     Result := Result + Item;
end;