[fpc-devel] Class extension

[Matt Emson]

Jonas Maebe wrote:
> Having implemented support for Objective-C/Pascal categories in the 
> compiler, I don't think that this concept can be translated to the 
> (Delphi-compatible) Object Pascal model/implementation. It only works 
> in Objective-C/Pascal because there all dispatching is based on the 
> name of the method/selector (instead of based on VMT offsets or static 
> binding).

I figured it would be pretty difficult to implement. It's definitely a 
nice feature though. Maybe as it matures, it might be possible to 
migrate and refactor?

> It may be doable with a separate class hierarchy (like 
> TInterfacedObject for COM) and compiler/RTL magic (that would probably 
> duplicate large parts of the Objective-C run time's functionality to 
> get everything running at a reasonable speed), but in that case it 
> might be more worthwhile to add support for GNUStep and extend the 
> Objective-Pascal support to all platforms (since it wouldn't work with 
> the regular Object Pascal classes in the RTL anyway). Objective-Pascal 
> and Object Pascal can be mixed in the same file, so you can use 
> delegation and other ways to bridge the two kinds of classes.

I wonder how easy it would be to do something with the Cocotron runtime? 
It is geared to being compiled on Mac, but uses a MINGW based cross 
compiler to target Windows and also compiles to target LINUX and BSD. 
The compiled library binaries should be movable to Windows at least. It 
also uses a more Cocoa like runtime mechanism than the GNUStep one. I 
don't remember all the technicalities, but there is a difference that 
was fairly important. That's probably a little vague, but I have a head 
cold and feel a bit groggy today ;-)

Food for thought.

M