[fpc-pascal]self

[Jonas Maebe]

On woensdag, okt 23, 2002, at 12:09 Europe/Brussels, Ingmar Tulva wrote:

> type
>   t1 = object
>     procedure p(var s:t1);
>   end;
>
>   t2 = object(t1)
>     {some fields here}
>   end;
>
> procedure t1.p (var s:t1); { or "const" or ^t1 }
>  begin
>    Self:=s;
>  end;
>
> var
>   o1,o2 : t2;
>
> begin
>   ---
>   o1.p(o2);
>   ---
> end.
>
> Will the additional fields of t2 be assigned or not?

I don't think the above will even compile, because var parameters must 
match exactly. Anyway, the extra fields cannot be assigned, because 
they don't exist in t1 (so there is no memory available to put them in).

> If not, then what is
> the use of this feature (assigning something to Self)?

You can replace the values of all the fields of an object with those of 
another object inside a method (this is important, because when you're 
outside a method, you can simply assign one object to another) without 
having to type all the fields explicitely.


Jonas