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  • A TclOO question

    From Helmut Giese@hgiese@ratiosoft.com to comp.lang.tcl on Sat May 17 22:57:56 2025
    From Newsgroup: comp.lang.tcl

    Hello out there,
    say I have a class and 2 instances like so

    oo::class create MyClass {
    constructor {someVal} {
    my variable myVar
    set myVar $someVal
    }
    method get {} {
    my variable myVar
    return $myVar
    }
    method set {val} {
    my variable myVar
    set myVar $val
    }
    }

    MyClass create obj1 33
    MyClass create obj2 99

    How can I set a trace on 'myVar' of 'obj2'?
    I found an example on the doc of the 'my' command but it sets a trace
    on a global variable during which an object is invoked - which doesn't
    fit my situation
    Any help will be greatly appreciated
    Helmut
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  • From Rich@rich@example.invalid to comp.lang.tcl on Sun May 18 01:31:06 2025
    From Newsgroup: comp.lang.tcl

    Helmut Giese <hgiese@ratiosoft.com> wrote:
    Hello out there,
    say I have a class and 2 instances like so

    oo::class create MyClass {
    constructor {someVal} {
    my variable myVar
    set myVar $someVal
    }
    method get {} {
    my variable myVar
    return $myVar
    }
    method set {val} {
    my variable myVar
    set myVar $val
    }
    }

    MyClass create obj1 33
    MyClass create obj2 99

    How can I set a trace on 'myVar' of 'obj2'?
    I found an example on the doc of the 'my' command but it sets a trace
    on a global variable during which an object is invoked - which doesn't
    fit my situation
    Any help will be greatly appreciated
    Helmut

    From outside the object, one way is, after you create the objects:

    Get the object's namespace:

    % info object namespace obj2
    ::oo::Obj13

    Then infer the location of the variable:

    % set ::oo::Obj13::myVar
    99

    Setting a trace on ::oo::Obj13::myVar should be trivial now.

    From inside one of the object's methods, the 'my varname' gives you the
    full namespace name:

    oo::class create MyClass {
    constructor {someVal} {
    my variable myVar
    set myVar $someVal
    }
    method where {} {
    puts "myVar is at [my varname myVar]"
    }
    }
    ::MyClass
    % MyClass create obj1 33
    ::obj1
    % obj1 where
    myVar is at ::oo::Obj12::myVar
    %

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  • From Helmut Giese@hgiese@ratiosoft.com to comp.lang.tcl on Sun May 18 19:03:23 2025
    From Newsgroup: comp.lang.tcl

    Hello Rich,
    many thanks for this simple explanation. I knew how to access procs in
    a namespace but hadn't quite realized that the same holds for
    variables - which looks obvious now :(
    Best regards
    Helmut
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