I want to pass an object from inside its own method to a helper function.
(I'd also like to know how to pass a bound method.)

In the example below I have tried using [self] and [self object] and [self
namespace] but none of them works.

#!/usr/bin/env wish9
tk appname "Test App"
proc make_file_menu {app} {
.menu.file add command -command {$app on_quit} -label Quit \
-underline 0 -accelerator Ctrl+Q
} oo::class create App {
constructor {} {
wm withdraw .
wm title . [tk appname]
grid [ttk::button .quitButton -text Quit -underline 0 \
-command [callback on_quit]]
bind . <Escape> [callback on_quit]
bind . <Alt-q> [callback on_quit]
menu .menu
menu .menu.file
.menu add cascade -menu .menu.file -label File -underline 0
make_file_menu [self] ;# BUG what do I pass here as "this"
. configure -menu .menu
}
method on_quit {} {destroy .}
method show {} {
wm deiconify .
raise .
}
} set application [App new]
$application show

The error I get is:

can't read "app": no such variable
while executing
"$app on_quit"
invoked from within
".#menu.#menu#file invoke active"
("uplevel" body line 1)
invoked from within
"uplevel #0 [list $w invoke active]"
(procedure "tk::MenuInvoke" line 49)
invoked from within
"tk::MenuInvoke .#menu.#menu#file 1"
(command bound to event)

I worked out how to do it:

proc make_file_menu {app} {
.menu.file add command -command [list ${app}::my on_quit] \
-label Quit -underline 0 -accelerator Ctrl+Q
}

For the caller I used:

make_file_menu [self]

On 11/07/2024 12:03, Mark Summerfield wrote:
> I worked out how to do it:
>
> proc make_file_menu {app} {
> .menu.file add command -command [list ${app}::my on_quit] \
> -label Quit -underline 0 -accelerator Ctrl+Q
> }
>
Or less hacky:

proc make_file_menu {app} {
.menu.file add command -command [list $app on_quit] \
-label Quit -underline 0 -accelerator Ctrl+Q
}

Originally you had $app inside curly braces, which prevented it from
being substituted at definition time. At execution time, the app
variable was out of scope.

Schelte.

On Thu, 11 Jul 2024 13:12:52 +0200, Schelte wrote:

[snip]
> Or less hacky:
>
> proc make_file_menu {app} {
> .menu.file add command -command [list $app on_quit] \
> -label Quit -underline 0 -accelerator Ctrl+Q
> }
>
> Originally you had $app inside curly braces, which prevented it from
> being substituted at definition time. At execution time, the app
> variable was out of scope.

Thank you, that works great.

* Mark Summerfield <mark@qtrac.eu>
| On Thu, 11 Jul 2024 13:12:52 +0200, Schelte wrote:
| > proc make_file_menu {app} {
| > .menu.file add command -command [list $app on_quit] \
| > -label Quit -underline 0 -accelerator Ctrl+Q
| > }
| >
| > Originally you had $app inside curly braces, which prevented it from
| > being substituted at definition time. At execution time, the app
| > variable was out of scope.
>
| Thank you, that works great.

To save you trouble on your TCL-road ahead, make sure you understand the
difference between

-command {$app on_quit}

which you had originally in your code and

-command [list $app on_quit]

which is the correct way of doing things and

-command "$app on_quit"

which also most probably would "work" right now,
until some day it won't :-)...

HTH
R'