Sept 26, 2005 See http://tip.tcl.tk/257
SUMMARY
TIP #257 is a proposal to put a small-but-powerful object-oriented programming system into the Tcl core (for 8.5) where everyone will be able to rely on it. Its feature set is to be based mostly on XOTcl, but with the addition of features for improved support for being the core of Snit. It should also be usable on its own.
IMPLEMENTATION NOTES
DKF 19 Aug 2006: There is now a partially working version of the tip257 implementation for people to test out. It is at about the point where you can create an object, give it some methods, and run the methods. However, constructors, destructors and inheritance do not yet work.
To get the source code, you need to check out the branch of CVS that I'm using for the development. You want to get from the usual tcl repository, but you want the branch tip-257-implementation-branch. Thus, assuming you've just got anonCVS access, you do this (the anon password is empty in case you're wondering, and the second line is split):
cvs -d:pserver:[email protected]:/cvsroot/tcl login cvs -d:pserver:[email protected]:/cvsroot/tcl -z9 co \ -r tip-257-implementation-branch -d tcl-and-tip257 tcl
Building on both Unix and Win should be supported (no idea about OSX). There is a (small) test file in the Tcl test suite, oo.test. If you want to know to basically use the code, look there first as the code passes the test now. No proper docs yet; use the TIP itself there for the moment.
Example session:
% oo::object create foo
::foo
% oo::define foo {method bar {} {puts "Hello, World!"}}
% foo
wrong # args: should be "foo method ?arg ...?"
% foo ?
unknown method "?": must be bar or destroy
% foo bar
Hello, World!
% oo::define foo {method spong {} {my bar; next}}
% foo spong
Hello, World!
no superclass method implementation
% set errorInfo
no superclass method implementation
while executing
"next"
(method "spong" line 1)
invoked from within
"foo spong"DKF 20 Aug 2006: Constructors now work (but there's only one meaningful class to use them on). On the down side, now know that the global command doesn't work in methods and constructors properly... (now fixed)
DKF 21 Aug 2006: Destructors, method forwarding (which used to crash), export and unexport now all added. There seems to be some kind of intermittent crash in the destructor code, probably due to memory not being managed quite right, but it doesn't crash on my home machine so tracking it down is slightly awkward. Export and unexport work, but won't work once we get inheritance in, especially in the MI case. Need to rethink how to implement them. :-(
OK, the destructor crash has been pinned down as being due to destructors firing when the OO system as a whole is going away. That degree of cleanup isn't something I've attempted to do yet.
DKF 23 Aug 2006: Single inheritance now working (or a good approximation of it; it's passing several tests).
RLH Is it the intention then of only allowing single inheritance and not multiple to avoid the "diamond" effect of inheritance? Or is this just a step in that direction?
DKF 24-25 Aug 2006: Multiple inheritance (diamond effects resolved using XOTcl rules) now working. Still got filters and mixins to do, but they're simple extensions of MI. (Does this answer your question, RLH? :-)) RLH Indeed it does. : )
DKF 26 Aug 2006: Most of object and class teardown now implemented. Memory leaks should be largely (but not yet completely) banished.
DKF 27 Aug 2006: Teardown now done, allowing more of test suite to pass. Filters now supported on objects (not class-wide).
DKF 28 Aug 2006: Per-object mixins and changing-an-object's-class now done. Mainly introspection facilities left in the C part of the development of this functionality. RLH You *are* sleeping I hope. : )
DKF 28 Aug 2006 (no, 29 Aug; it's late): Partial implementation of object cloning. Method cloning not working right, and class cloning completely wrong. (And I do this instead of watching television, which is why I have so much time.) RLH I haven't had television for 12 years now. : )
DKF 29 Aug 2006: Fixed crashes that were stopping the test suite from passing on Linux. They were caused by trying to run destructors in an interpreter which was cleaning up (a bad thing!), what happens when an object is deleted the "wrong way round" and the complex tangle of what happens when the object system core goes away. Thanks to dgp for helping me debug this.
DKF: 30 Aug 2006: Added the start of the introspection facilities called for in the TIP.
DKF: 31 Aug 2006: Non-class object cloning done.
DKF: 02 Sep 2006: Class cloning done, and oo::definer metaclass implemented. All current tests pass, so what's left are believed to be sins of omission.
DKF: 17 Sep 2006: Nearly finished the oo::struct class.
DISCUSSION
Moved to TIP #257 Discussion.
TESTING
MJ - I am playing around with the new functionality to get a feel for it. To do this I am porting some code from XOTcl to tip OO. When using constructors I don't seem to be able to define multiple instance variables. Am I doing something wrong in the code below?
oo::class create Test {
constructor {args} {
variable a b
set a [lindex $args 0]
set b [lindex $args 1]
}
}
set a [Test new a b]
info object $a vars
# returns a, I would have expected {a b} to be returned