🚀 go-pugleaf

"Dana Dill" <dana@danadill.com> wrote in message
news:3ddd61dd$1@newsgroups.borland.com...
> myVar := SomeFunc(Parm: Type): TObject;
>
> I want "myVar" to be a copy of the object and not a pointer.  "myVar" is a
> local var and when it gets freed it of course frees the assigned object as
> well (Which is really the same. <g>)

Variables that "contain" object instances are always pointers. They are
implemented in current Delphi versions as 32-bit wide pointers to the actual
object. Nothing prevents you from writing code that creates a new object and
returns this as a result.
In other words:

MyObject:=TSomeClass.Create;

will create an new instance of TSomeClass and MyObject will contain a
pointer to that instance. If you create an object, you are responsible for
freeing it after you're done with it. SO, if you do the following:

var
  MyObject: TSomeClass;
begin
  MyObject:=TSomeClass.Create;
  ...
end;

The instance of TSomeClass that you created never gets freed. The "MyObject"
variable will go out of scope at the end of the procedure block, hence will
be freed (it is actually implemented on the stackframe). So, the reference
to the object you created is gone, but the object itself still exists (and
since the only reference to it just went out of scope, you can't even free
it anymore).
By using Interfaces, rather than classic Delphi classes, however, you can
leave some of the lifetime maintenance of your objects to be handled by the
compiler (through reference counting, similar to how long strings are
managed - after all, long string variables are mere pointers to the actual
string as well). Interfaces come with an additional overhead, so use them
only when appropriate. You'll find all relevant information in online help
and a google search for some examples is usually helpful too.

Guido


--
Guido Gybels
http://www.optimalcode.com/Guido
(Disclaimer: all remarks made apply to Intel processors unless specified
otherwise)