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From: Christian Gollwitzer <auriocus@gmx.de>
Newsgroups: comp.lang.tcl
Subject: Re: try... query
Date: Fri, 6 Dec 2024 18:37:25 +0100
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Am 06.12.24 um 14:11 schrieb Alan Grunwald:
> I'm attempting to get my head around preventing resource leaks, using 
> try and return.

I haven't worked through your code, but in C++, there is a great idiom 
called RAII - things get destroyed when the variable goes out of scope. 
This can be simulated for Tcl using a delete trace on the variable.
Using the little utils package from here: 
https://github.com/BessyHDFViewer/BessyHDFViewer/tree/main/bessyhdfviewer.vfs/lib/SmallUtils

You can do this for files:

proc something {} {
	SmallUtils::autofd fd somewfile w
	puts $fd "Text comes here"
}
# fd goes out of scope, file is closed

and for any objects that work Tk-like, giving a command back:


SmallUtils::autovar btn button .b -text "Hi"
# will destroy if btn goes out of scope
# by "rename .b {}"


Of course, this is not perfect, it will fail if you copy the variable 
somewhere else, but often times it is good enough.

                Christian