Pointer to Function of (Sub-)Method?

Question

If you like to use a method's pointer as an argument, you need to type the method as function of object like this works good:

type TAcceptor = function(filename:string):boolean of object;
function acceptor(filename:string):boolean; 
begin 
  result := filename <> ''; 
end;

What if you like to use the pointer of a sub-method? It does not work:

procedure TForm1.Button1Click(Sender:TObject);
  function acceptor(filename:string):boolean of object;
  begin 
    result := filename <> ''; 
  end;
begin
end;

The error occour: ; expected but OF found!

Question: Is there any subfunction-pointer? Can i cast it?

Answer 1

I don't see how that this would be possible.

http://docwiki.embarcadero.com/RADStudio/XE6/en/Procedural_Types

If you look under the method pointers section, it specifically says that nested procedures and functions cannot be used:

"Nested procedures and functions (routines declared within other routines) cannot be used as procedural values, nor can predefined procedures and functions."

You might be able to work around it using an anonymous method. Something like:

procedure TForm1.Button1Click(Sender:TObject);
begin
  DoSomethingWithAcceptor(function(FileName: string): Boolean
  begin 
    Result := FileName <> '';
  end);
end;