OOP_(re)

Tue, 27 May 1997 17:59:50 -0400 (EDT)

On Mon, 26 May 1997, The African Chief wrote:

> The TObject type as I implemented it in OBJECTS.PAS has
> a number of fields;
> 	"Parent" and "Child" (each declared as a "pObject")
> 	"Handle" and "SelfID" (each declared as an Integer)
> 	"Name" (declared as a String[64])
> 	"SelfPtr" (private field declared as a "pObject")
> 
> At the moment, "Parent" and "Child" do nothing, and "Handle" is
> for projected future use (for handles to windowed objects - Win32, etc).

Well, this is *exactly* what object-orientation is there for, so you add
the fields when you need them. TObject itself is a "do-nothing" object. As
such, it is *not* windowed and should *not* have any Handle field as it
won't ever have ANYTHING in it! A TWindow descendent shall add this field.

> "SelfID" is an integer which holds a unique numeric ID for each 
> living TObject descendant.

Does this have any projected use?

> Can we make TObject automatically become the ancestor of each Object
> type (i.e., any object which is just defined as "Object")?; if so, is
> this desirable?; if so, can this solve any of the current problems with
> Streams and stuff? 

This is not really desireable. This will only impose on people our TObject
structure. I have a different TObject and Turbo Vision has a different
TObject and we can both live together with the same compiler (of course,
don't use both Units!) without any problem. It wouldn't solve anything
regarding streams anyway...

> I would have thought that some of the fields declared in TObject could
> be put to better use than I have done so far - and that more fields
> could be added to TObject, to cater for other things (i.e., if TObject
> will become the ultimate ancestor of all Object types). 

Posted on this list is the OBJECTS.PAS unit from Free Vision (the object
library of FPK-Pascal). It is *not* a better object library, but it is a
good compatible unit adapted to works correctly in 32-bit. *Very*
conforming, they even put the friggin' Free method with a "god I hate
this" comment... :-)

Pierre Phaneuf

"The use of COBOL cripples the mind; its teaching should, therefore, be
regarded as a criminal offense." - Edsger W. Dijkstra.

Pierre Phaneuf (pp@dilu.ml.org)