- what
- Namespace names for incr Tcl
- problem
- incr Tcl expects that the namespace of a class is the same as the class name
- solution
- Add an option -withnamespace or a method createwithnamespace
- what
- calling of methods without my in front of the method name
- problem
- incr Tcl resolves command calls first within the class hierarchy before using the normal Tcl rules
- solution
- Add a namespace unknown command as a dispatcher for incr Tcl methods
- what
- access to class variables
- problem
- incr Tcl has 3 protection levels which guard the access to class variables in the class hierachy.
- solution
- I use the apply command for constructing the body parts for the class methods (and [constructor]s and [destructor]s) after the complete class has been parsed and all classes in the hierarchy are known. There is an additional parameter, self, added automatically to the arguments of the method, and the variables of all the classes in the hierarchy are mapped using namespace upvar. Variables in incr Tcl have to live in the namespace where they are defined as there might be the same variable name in different classes in the hierarchy even with different protection (private, protected and public). In generating the namespace upvar commands the private variables of inherited classes are skipped.
set self [self]APW 2007-06-10: looks ok, I will try that.
- what
- incr Tcl rules for calling/traversing the constructors and destructors
- problem
- The rules for traversing the constructors/destructors in incr Tcl are very "special" and cannot be mapped to the model in tclOO. Example:
class foo {
constructor {args} { puts foo }
}
class bar {
constructor {args} { puts bar }
}
class foobar {
superclass foo bar
constructor {args} { puts foobar }
}
class geek {
constructor {args} { puts geek }
}
class mongrel {
superclass foobar geek
constructor {args} { puts mongrel }
}
output: geek bar foo foobar mongrelIn other words incr Tcl walks through the list of superclasses starting at the end based on the definition order. It looks for inherited classes up to the root class and unrolls the built stack. Then for the next class in inheritance, the same is done.- solution
- New command: "invokeitclconstructors" similar to the [next] command in tclOO (to be done: add details here)
% package req TclOO; namespace path oo
% class create foo { constructor {} {next; puts foo} }
::foo
% class create bar { constructor {} {next; puts bar} }
::bar
% class create foobar { superclass foo bar; constructor {} {next; puts foobar}}
::foobar
% class create geek {constructor {} {next; puts geek}}
::geek
% class create mongrel {superclass foobar geek; constructor {} {next; puts mongrel}}
::mongrel
% [mongrel new] destroy
geek
bar
foo
foobar
mongrelDKF: Discussion seems to indicate that there is a deeper problem here, but not one I understand yet.APW: I need info class superclasses ... on a lot of places for incr Tcl and it returns the class names not in the order the have been defined, so I am calling class create mongrel {superclass geek foobar; constructor {} {next; puts mongrel}}to get the order as expected in incr Tcl, for the incr Tcl input: itcl::class mongrel { inherit foobar geek; constructor {} {puts mongrel}}DKF: Ah, I don't provide any code to walk the whole superclass hierarchy and describe it. Perhaps I should; it could leverage information stored at the C level very nicely, and so be a lot more efficient than a Tcl-implemented version.- what
- incr Tcl special init code script in constructors
- problem
- In incr Tcl constructors it is possible to define an init script, which is invoked directly before the code in the constructor, but after the object is instantiated. Example:
The script after the arguments and before the body is the "constructor init code"
class foo {
constructor {args} { puts foo }
}
class bar {
constructor {args} { puts bar }
}
class foobar {
superclass foo bar
constructor {args} {
foo::constructor ; # this is the init code which calls the constructor of class foo
} { puts foobar }
}
class geek {
constructor {args} { puts geek }
}
class mongrel {
superclass foobar geek
constructor {args} {
foobar::constructor
} { puts mongrel }
}
output: foo bar foobar geek mongrel- solution
- Add the init code script in building the apply code for the constructors
- what
- incr Tcl command itcl::body
- problem
- In incr Tcl, there are several ways to partially define a method: protection + name, protection + name + params, protection + name + params + body. That method can be redefined later on, but the params list for the method - if defined in the class definition - has to be compatible.
- solution
- Add additional information about method params and status to each method definition in the tclOO internal structures. There is an additional problem in that tclOO cannot handle partially defined methods, the solution to which is adding this functionality.
- what
- incr Tcl info command
- problem
- Getting the original body of a method when using apply internally
- solution
- Save the original body in the tclOO internal structures of a method. In general I am generating a method info within each class. That is like a class proc in incr Tcl syntax. It is something like a singleton method and it can be called without an object being instantiated. info first trys the incr Tcl specific commands, and if that does not work, it forwards to the ::info command.
- what
- incr Tcl singelton methods
- problem
- In incr Tcl it is possible to have class methods which are like singletons. They can be called uisng the class or an instantiated object. Nevertheless, if they have protection level protected they can be only called from within the class namespace. That will not work with the current tclOOCall.c implementation, as it just calls unknown and also if that is a user defined method, there is not enough information available for specific diagnostics.
- solution
- Add some code in AddMethodToCallChain, to do some additional checks and use a class specific call back to report the appropriate error.
- Put them as procedures in the class's namespace (you won't be treating the class as an object from the incr Tcl view)
- Use namespace path to splice in (but be aware that there is already an existing path)
- what
- incr Tcl method calls and protection violation errors
- problem
- In incr Tcl it is necessary to generate specific error messages when a protection violation is detected. That will not work with the current tclOOCall.c implementation.
- solution
- Add some code in AddMethodToCallChain, to use a class-specific call back in that case, which can be set via a setprotectioncallback command, to report the appropriate error.
- what
- Calling incr Tcl methods
- problem
- In incr Tcl when calling a method it is expected that the method runs in the class namespace with the variables of the class and all inherited (and accessible) variables to be mapped into that namespace temporarly for the call.
- solution
- In creating classes allow a parameter namespace for the AllocObject method, which is NULL for the "normal" tclOO system and is != NULL for generating classes for incr Tcl (that needs also changes for "class create"). This namespace is used later on in InvokeProcedureMethod if != NULL, which fits for incr Tcl calling methods and also to allow the class to have the same namespace as the class name (see also what: Namespace names for incr Tcl)
if (tobjPtr->selfClsPtr->thisPtr->namespacePtr != NULL) {
/* use the classes namespace if it exists for example for [incr Tcl] */
namespacePtr = tobjPtr->selfClsPtr->thisPtr->namespacePtr;
} else {
namespacePtr = tobjPtr->namespacePtr;
}The variables of the different classes are mapped (if accessible) using the "namespace upvar" command (that code is inserted in the body of a method at the very beginning), when the class is completely parsed. The path for that "namespace upvar" command is handled using the self variable in the method parameters (see above). This allows the methods to be compiled once only for performance on the very first call to a class method.DKF: This feels very much like something best achieved through custom method types. All this stuff can be controlled easily at that level.APW 2007-06-10 - But then I will also need an own InvokeProcedureMethod function, so most of the method handling is the done without tclOO :-( .DKF: I'm open to actually hosting support code so that you don't need to worm yourself in deeply to the guts of Tcl (the IPM implementation is non-trivial since it splices itself into the heart of proc at a point that didn't exist before 8.5).APW 2007-06-10: I have seen the differences in IPM , which are necessary for info frame command, I am a little bit familar with the part, as I have played around and debugged quite some time in that function and the called functions in the past to get my code working, so problem with IPM seems to be not so big for me. I especially had problems with the old (before info frame) error handling, as I had invented some new flags for incr Tcl which made the old implementation core dump. RenderDeclarerName etc. look much more readable for me, and you directly see what happens here. Had also to look into TclProcCompileProc and TclObjInterpProcCore for the same reason, so I have an approximate idea what's going on there.APW 2007-06-11 have reorganized the "callback" topic for better understanding.
- what
- detecting calls to non-accessible method
- problem
- In incr Tcl it is necessary to give a specific error message, if a non-accessible method is called
- solution
- enhancing the calling mechanism of tclOO to allow installing a callback function on an per object base which is called instead of the current accessible checking code:
/*
- Enforce real private method handling here. We will skip adding this
- method IF
- 1) we are not allowing private methods, AND
- 2) this is a private method, AND
- 3) this is a class method, AND
- 4) this method was not declared by the class of the current object.
*
- This does mean that only classes really handle private methods. This
- should be sufficient for incr Tcl support though.
*/
if (!(contextPtr->flags & PRIVATE_METHOD)
&& (mPtr->flags & PRIVATE_METHOD)
&& (mPtr->declaringClassPtr != NULL)
&& (mPtr->declaringClassPtr != contextPtr->oPtr->selfCls)) {
return;
}This code is currently found in tclOOCall.c in function AddMethodToCallChain. I would like to have a functionality which is calling an installed (from the application user) callback instead of that code (if it exists). The logic would be: in the above code there is a return if the check for accessibility fails, the callback should return a NULL if the accessibility fails, in that case AddMethodToCallChain would also return as in the above code. Otherwise it returns a mPtr. mPtr is either the parameter which has been given to the callback as parameter if the accessibility is ok or (if desired) another mPtr, which must be the structure for a method also defined in that object/class. In that case the rest of the code is executed as before. The new method can then handle the generation of an appropriate error message if the execution comes to that point, or do whatever is wanted in that case, for example do some forwarding.APW 2007-06-09 - @DKF: after spending some thoughts on your answers I have the feeling there will not much I can use directly from tclOO. Using custom method types, I will need my own InvokeProcedureMethod and then I can directly pass all the needed data via clientData to my InvokeProcedureMethod. So there will be no further need to use the metadata mechanism, as that would be more overhead to call it. For the info stuff I will nevertheless need my own code, as it is so different to tclOO info. For constructors and destructors - as you suggested - I will need my own code. To handle protection violation - as you suggested - I will need my own code. So what I can use from tclOO would mostly be creation, administration and deletion of classes and objects. I cannot use tclOOCall.c, because I need additional information (and the special code to provide in there the checking of protection violation), I will not need tclOODefineCmds.c, as I directly call the tclOO API functions, I will not need tclOOInfo.c (see above). That was not my intention! I would like to use much more of it! I like the implementation of tclOOCall.c, but at least for incr Tcl (maybe also for others) it is too limited at the moment. Do you have any better ideas? -- APW 2007-06-11 -- no longer relevant, there have been enhancments for tclOO and other ideas from me see below.DKF: Right now, I don't understand enough to know exactly what additional APIs are needed. This is a large part of why we (myself and others) decided that TclOO had to go for a round of usage as an extension rather than going straight in as part of Tcl. I want to understand how to fix these problems; I've just not yet understood.APW 2007-06-10: In the meantime I have looked for a different solution for some of the problems I have. I have put all the stuff needed for "info" into some dicts (in Tcl), so that part (if there are not big problems) is no longer a problem. For the incr Tcl calling problems (without my in front) I have today implemented a namespace command resolver, which also avoids the problems I had with namespace unknown. I am building dicts for method access per class including all the superclasses and have access to that information in the C-part (really cool what is able with dicts). What I am not sure is if dicts are about equally fast as using the class and superclasses with the hash tables. I am using the dicts as the hashtables for methods and the lists for superclasses are not in the API.APW 2007-06-11: So after all, I think the "big" problems still remaining are the callback mechanism described above and a possibility for using the class namespace in InvokeProcedureMethod instead of the object namespace.APW 2007-06-18: After the implementation of functionality for using the class namespace in InvokeProcedureMethod (thanks to DKF), the remaining callback problem seems to be doable by a small additional API interface, which I have suggested to DKF. I will now continue to make the implemention more complete, to see what is left over as a problem (nothing at the moment).
APW 2007-06-10: have removed the following part, which included some suggestions for the layout, as that is no longer necessary.
