TIP #354: Minor Production-Driven TclOO Revisions

Title:Minor Production-Driven TclOO Revisions
Version:$Revision: 1.4 $
Author:Donal K. Fellows <dkf at users dot sf dot net>
Created:Wednesday, 26 August 2009


This TIP describes a few small changes required for solving issues that have been found when using TclOO in production.


TclOO (see TIP #257) has now had a substantial amount of use for relatively complex functionality (as well as production deployment) and it has turned out that there were a few small changes required.

  1. The scope of resolution for the target of a forwarded method is updated so that it is with respect to the object's namespace. This means that a class may create methods that forward to a command given by each instance, which makes creating megawidgets by wrapping real Tk widgets much easier, since the forwards do not have to be created at the instance level.

  2. A subcommand was added to info object to allow the discovery of the namespace of an object by code outside that object. This makes it far easier for code that needs to "break the abstraction" to do so, which turns out to be necessary for things like serialization. This subcommand, namespace, takes an object name as its only argument and returns the name of the object's namespace.

    To expand on the requirements for serialization, the serialization code needs to call a method on each object to create the serialization for that object. However, the method should not be part of the public API for the object as it cannot perform a complete serialization correctly, since the serialization depends on the rest of the object graph. (It also requires a number of global overheads that are best applied once, not repeatedly.)

    Note that I plan to release the serialization code itself (originally developed as part of a solution for a Rosetta Code task) as a package via tcllib. This TIP does not propose its inclusion with Tcl.

  3. A new C API function has been added to allow code at that level to efficiently discover the name of an object that it already has a handle to. This new function, Tcl_GetObjectName, returns a shared Tcl_Obj reference to the name that needs no special reference count management.


This document has been placed in the public domain.

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