Michel Fortin wrote:
On 2009-01-31 18:50:52 -0500, Walter Bright <[email protected]>
said:
Michel Fortin wrote:
One area I think Objective-C to be very great and that you haven't
touched is for creating stable APIs. In Objective-C, contrary to D
and C++, you don't have to recompile every dependency when
reordering, adding and removing member functions in a class. In
64-bit Objective-C 2.0, you can even add variables to a class without
care about recompiling derived classes. Compare that to D, where
exposing a class as a public API will either force you to not change
much that class, or force your users to recompile every time you make
such a change.
If you use interfaces, you can add member fields without needing to
recompile clients.
Yeah, indeed. I hadn't thought about that. That's a pretty interesting
thing about interfaces now that you make me think about it.
But exposing only interfaces makes the API harder to use. In Cocoa,
classes gain new methods at each new version of the framework (read each
version of Mac OS X) and it doesn't hinder programs compiled with
earlier versions of the framework.
If you had a smart enough dynamic linker and the signature of each
function in the virtual table, you could do that in D too by creating
virtual tables and updating offsets in the code accordingly while
linking. (Objective-C doesn't work like that, but it has the same
effect.) Alternativly, it could be done in some static initialisation
phase.
An increasingly interesting toy to study (I would think) would be
Categories - the ability to take an existing class and just randomly
tack on additional receivers. Perhaps this is exclusive to
Objective-C's message-receiver architecture, but it's a curious little
technology nonetheless.
