TIP 473: Allow a Defined Target Namespace in oo::copy

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State:		Final
Type:		Project
Tcl-Version:	8.6.7
Vote:		Done
Post-History:	
Author:		Donal Fellows <dkf@users.sf.net>
Created:	06-Jun-2017
Keywords:	Tcl, missing functionality, bugfix
Tcl-Branch:	oo-copy-ns

Abstract

This TIP adds functionality to oo::copy to allow the created copy to have a defined namespace, much as oo::class's createWithNamespace method allows such a namespace to be given on normal object creation.

Rationale

Due to an oversight, the oo::copy command is missing the ability to have an explicit namespace name specified to use as the instance namespace of the target object. It was always intended to have this (and the functionality is there in the C API), but it was omitted from the Tcl-level interface.

Having this capability allows objects to be used as factories for namespaces, which is in many ways an inversion of the way that TclOO was designed (with namespaces as the basis for objects). It was requested by Nathan Coulter as a way to enable more complex behaviour in Rivet and NaviServer. See Tcl Issue dd3b844fda http://core.tcl.tk/tcl/tktview/dd3b844fdabdeae5fcb0 for more information.

Proposed Change

I propose to add one more optional argument to oo::copy, targetNamespace, that if provided and non-empty will be the name of a namespace (resolved relative to the current namespace if not an absolute name) that will be the name of the newly created target object's instance namespace. The named namespace must not already exist. Note that specifying the targetObject as the empty string will cause the object's command to be automatically chosen.

oo::copy sourceObject ?targetObject? ?targetNamespace?

The meaning of the result of the command is unchanged.

Implementation

See the oo-copy-ns branch. http://core.tcl.tk/tcl/timeline?r=oo-copy-ns

Copyright

This document has been placed in the public domain.