Question

I’m writing a class with some virtual/abstract procedures which I expect to get overridden. However they might not be overridden as well, which is also fine. The problem is finding out whether one of these procedures was actually overridden or not. If they’re not overridden, I shouldn’t try to call those procedures, and need to go about something different instead. If I try to call one of them and isn’t overridden, I get Abstract Error.

Is there a way I can detect whether these procedures were overridden or not?

Here’s a sample of how they’re declared:

type
  TMyClass = class(TObject)
  protected
    procedure VProc; virtual;
    procedure VAProc; virtual; abstract;
  end;

Answer 1

You can do something like this. Note that I’ve removed “abstract”. It may work with “abstract” in place, but I haven’t tried that.

type 
  TMyClass = class(TObject) 
  protected 
    procedure VProc; virtual; 
    procedure VAProc; virtual; //abstract;
  end; 


function GetVAProcAddress(Instance: TMyClass): pointer;
var
  p: procedure of object;
begin
  p := Instance.VAProc;
  result := TMethod(p).Code;
end;


//in one of the TMyClass methods you can now write:

  if GetVAProcAddress(self) <> @TMyClass.VAProc then