From Newsgroup: comp.lang.tcl

Given this class:

oo::class create App {
# ...
variable ShowState
}

And this method:

oo::define App method make_controls {} {
# ...
ttk::radiobutton .controlsFrame.showFrame.asIsRadio \
-text "Show as-is" -value asis -variable ShowState
set ShowState asis

The variable given to the radio button and the instance variable
are _different_.

I tried these variations, all of which gave errors:

-variable [my ShowState]
-variable [my $ShowState]
-variable [self ShowState]
-variable [self $ShowState]

For now I'm using a global variable ::ShowState
but I'd really like it to be an instance variable -
if it can be done?
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From Newsgroup: comp.lang.tcl

At Fri, 11 Jul 2025 09:55:25 -0000 (UTC) Mark Summerfield <m.n.summerfield@gmail.com> wrote:

Given this class:

oo::class create App {
# ...
variable ShowState
}

And this method:

oo::define App method make_controls {} {
# ...
ttk::radiobutton .controlsFrame.showFrame.asIsRadio \
-text "Show as-is" -value asis -variable ShowState
set ShowState asis

The variable given to the radio button and the instance variable
are _different_.

I tried these variations, all of which gave errors:

-variable [my ShowState]
-variable [my $ShowState]
-variable [self ShowState]
-variable [self $ShowState]

For now I'm using a global variable ::ShowState
but I'd really like it to be an instance variable -
if it can be done?

I don't know anything about how Tcl OO system works, but with SNIT I can do this:
package require snit
package require Tk
snit::widget foo {
variable ShowState
constructor {args} {
# ...
ttk::radiobutton $win.controlsFrame.showFrame.asIsRadio \
-text "Show as-is" -value asis -variable [myvar ShowState]
# ...
}
}

--
Robert Heller -- Cell: 413-658-7953 GV: 978-633-5364
Deepwoods Software -- Custom Software Services
http://www.deepsoft.com/ -- Linux Administration Services
heller@deepsoft.com -- Webhosting Services
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From Newsgroup: comp.lang.tcl

On 11/07/2025 11:55, Mark Summerfield wrote:

Given this class:

oo::class create App {
# ...
variable ShowState
}

And this method:

oo::define App method make_controls {} {
# ...
ttk::radiobutton .controlsFrame.showFrame.asIsRadio \
-text "Show as-is" -value asis -variable ShowState
set ShowState asis

The variable given to the radio button and the instance variable are_different_.

ttk::radiobutton .controlsFrame.showFrame.asIsRadio \
-text "Show as-is" -value asis -variable [my varname ShowState]


Schelte.

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From Newsgroup: comp.lang.tcl

On Fri, 11 Jul 2025 13:28:06 +0200, Schelte wrote:

On 11/07/2025 11:55, Mark Summerfield wrote:

Given this class:

oo::class create App {
# ...
variable ShowState
}

And this method:

oo::define App method make_controls {} {
# ...
ttk::radiobutton .controlsFrame.showFrame.asIsRadio \
-text "Show as-is" -value asis -variable ShowState
set ShowState asis

The variable given to the radio button and the instance variable
are_different_.

ttk::radiobutton .controlsFrame.showFrame.asIsRadio \
-text "Show as-is" -value asis -variable [my varname ShowState]

Schelte.

That silently didn't work.
I also tried `-variable [my variable ShowState]` and that didn't work
either.

I don't use snit so I couldn't use that approach either.

Given that Tcl 9 has the incredibly useful `callback` command
which I use all the time with Tk widgets for their `-command`
options, I'm surprised there isn't an equivalent for Tk widget
variables: or perhaps there is and I haven't found it?
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From Newsgroup: comp.lang.tcl

On 11/07/2025 17:21, Mark Summerfield wrote:

That silently didn't work.

Then you have a bug somewhere in the code you didn't show, because [my
varname ShowState] correctly produces the fully qualified name of the
instance variable.

Another way to get the fully qualified name of the variable is
[namespace which -variable ShowState]. But as that produces the same
result, it also won't work until you fix that other bug.


Schelte.

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From Newsgroup: comp.lang.tcl

On Fri, 11 Jul 2025 21:12:08 +0200
Schelte <nospam@wanadoo.nl> wrote:

...

Another way to get the fully qualified name of the variable is
[namespace which -variable ShowState]. But as that produces the same
result, it also won't work until you fix that other bug.

Adding to what Schelte correctly pointed out, these are your options:

* [my varname somevar]: This works inside TclOO objects, and works for scalar
variables, arrays and array elements.
* [namespace which -variable somevar]: This works inside TclOO objects and
namespaces. Works for scalar variables and arrays, but not for array
elements. See Tcl bug#472113 . If you need an array element, use
[namespace which -variable somearray](element).
* last but not least, [namespace current]::somevar works if somevar is
a variable in the current namespace, including the namespace of any TclOO
object, and works for scalar, array and array elements.

Regards
--
Emiliano
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From Newsgroup: comp.lang.tcl

On 7/11/2025 4:13 PM, Emiliano wrote:

On Fri, 11 Jul 2025 21:12:08 +0200
Schelte <nospam@wanadoo.nl> wrote:

...

Another way to get the fully qualified name of the variable is
[namespace which -variable ShowState]. But as that produces the same
result, it also won't work until you fix that other bug.

Adding to what Schelte correctly pointed out, these are your options:

* [my varname somevar]: This works inside TclOO objects, and works for scalar
variables, arrays and array elements.
* [namespace which -variable somevar]: This works inside TclOO objects and
namespaces. Works for scalar variables and arrays, but not for array
elements. See Tcl bug#472113 . If you need an array element, use
[namespace which -variable somearray](element).
* last but not least, [namespace current]::somevar works if somevar is
a variable in the current namespace, including the namespace of any TclOO
object, and works for scalar, array and array elements.

Regards

As a learning exercise,

I filled in Mark's code (added the 2 frames, a second radio button, and packed it up) and used the [my varname ...] form which worked for me.

Here's a little debug procedure one can use to find object variables. It might prove helpful. Note, the [my varname ...] will register the variable in the object's namespace, but the variable is still unset, which this code can show.



# Function to dump all object variables
proc dovar {{all 0} {sep "-----------------------------------"} } {
if { $sep ne "" } {
puts $sep
}
foreach ns [namespace children ::oo] {
if {[string match "Obj*" [namespace tail $ns]]} {
set objName ::$ns
set class "<unknown>"
catch {
set class [info object class $objName]
}
if {!$all && $class eq "<unknown>"} {
continue
}
puts "Object: $objName (Class: $class)"
foreach var [info vars ${ns}::*] {
set shortName [namespace tail $var]
if {[info exists $var]} {
catch { set val [set $var] }
} else {
set val "<unset>"
}
puts " $shortName ($var) = $val"
}
}
}
if { $sep ne "" } {
puts $sep
}
}


-eric

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From Newsgroup: comp.lang.tcl

On Fri, 11 Jul 2025 21:12:08 +0200, Schelte wrote:

On 11/07/2025 17:21, Mark Summerfield wrote:

That silently didn't work.

Then you have a bug somewhere in the code you didn't show, because [my varname ShowState] correctly produces the fully qualified name of the instance variable.

Another way to get the fully qualified name of the variable is
[namespace which -variable ShowState]. But as that produces the same
result, it also won't work until you fix that other bug.

Schelte.

Thank you (and the others) for your help.

The mistake I made was that I initialized the variable in the wrong place.
Now I call `set ShowState asis` in the constructor and use
`-variable [my varname ShowState]` and it all works fine.

When I looked at the docs for `my` I couldn't find `varname` but now
realise this is documented on the `oo::object` page.
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