duplicate an instance of an object

[DaZZleD]

In my project I use self created classes. I instantiate an object then when I create another one that equals the first, delphi actually creates the second as a pointer to the first. I would like to actually duplicate the object in memory, as a new instance... Is there any method for it, or do I have to create my own duplicate method that copies each of the attributes' values of the first object to the second?

 

[LucieLastic]

hi

I think the api call CopyMemory would do it. Also Delphi's Move procedure is worth a go. Delphi's example (I'm sure this should work with objects):-

var
A: array[1..4] of Char;
B: Integer;
begin
Move(A, B, SizeOf(B)); { SizeOf = safety! }
end;

lou

 

[towerbase]

Danny Thorpe's highly regarded book "Delphi Component Design" covers this on pages 205 - 210.

If your class descends from TPersistent then Assign support is provided.

The book gives an example of a simple implementation of Assign. I hope I'm not infringing copyright by reproducing it here.

procedure TStrings.Assign(Source: TPersistent);
begin
  if Source is TStrings then
  begin
    BeginUpdate;
    try
      Clear;
      AddStrings(TStrings(Source));
    finally
      EndUpdate;
    end;
  end else inherited Assign(Source);
end;

HTH

Andrew