Hello out there,
look at the following sample:
---
catch {Sample destroy}

oo::class create Sample {
variable classVar ;# automatically exists in every instance
constructor {someVar} {
my variable objVar
set classVar $someVar
set objVar 99
}
destructor {
my variable objVar classVar
puts "classVar: $classVar, objVar: $objVar"
}
}

Sample create s1 100
Sample create s2 200
s1 destroy ;# -> classVar: 100, objVar: 99
s2 destroy ;# -> classVar: 200, objVar: 99
---
My question is: What happens, if I add 'classVar', although not
needed, to a 'my variable' statement - like I did in the destructor
above. Is it just superfluous or can it have consequences in a more
complex situation than the above example.
Thank you for any enlightenment
Helmut

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Hello Helmut

AFAIK the varaible statement in the class context will fill a list.
This list is used to "upvar" your variables in the context of newly
created methods.
But beware. When you create new method in the object context with
oo::objdefine the list is not used. This means you have to manually call
the variable command.

HTH
rene

--

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Hello Rene,
thanks for your answer , it was really helpful
Helmut

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On 07.04.25 18:34, Helmut Giese wrote:

Hello out there,
look at the following sample:
---
catch {Sample destroy}

oo::class create Sample {
variable classVar ;# automatically exists in every instance
constructor {someVar} {
my variable objVar
set classVar $someVar
set objVar 99
}
destructor {
my variable objVar classVar
puts "classVar: $classVar, objVar: $objVar"
}
}

Sample create s1 100
Sample create s2 200
s1 destroy ;# -> classVar: 100, objVar: 99
s2 destroy ;# -> classVar: 200, objVar: 99
---
My question is: What happens, if I add 'classVar', although not
needed, to a 'my variable' statement - like I did in the destructor
above. Is it just superfluous or can it have consequences in a more
complex situation than the above example.
Thank you for any enlightenment
Helmut

a very good source for all kind of programming questions is the KI
for example the GROK from X(twitter)

→ https://x.com/i/grok

it is really impressive, here is your answer:

→ https://x.com/i/grok/share/Wo4XKUycnscf3WNTbpMoms93f

mfg

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Hi aotto.
that's really cool: a complete, detailed analysis which even I
understood. Many thanks for this link
Helmut

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* Helmut Giese <hgiese@ratiosoft.com>
| | → https://x.com/i/grok/share/Wo4XKUycnscf3WNTbpMoms93f
| that's really cool: a complete, detailed analysis which even I
| understood. Many thanks for this link

The text created by the AI contains a subtle error: it makes a
difference between "variable foo" at class level and "my variable foo"
at method level as the former being a "class-wide" variable (shared
across instances, 'static' in C++, 'common' in itcl) and the latter "instance-specific" ones (specific to one object):

[Complex situations, p2]
...
["my variable classVar" in method without previous "variable classVar" at class level]
...
In this case, classVar becomes an instance-specific variable, not a
class-wide one, which could lead to unexpected behavior if the
intent was to share classVar across instances.

As far as I understand it, this is not the case. Also the code you
posted cleary shows that classVar is *not* shared between instances
(each object has it's own value).

Maybe someone with more knowlegde on this can share some insight?

R'

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Not seen Grok's example but Tcl 9 does have class variables. See https://www.tcl-lang.org/man/tcl9.0/TclCmd/classvariable.html.


On 4/14/2025 9:35 PM, abu wrote:

Grok was very clever explaining the current code, but it was wrong
trying to depict a more complex case.

"classVar" is not a class-variable (despite its name).
Simply Tcloo has not (yet) a concept of class-variables. All the
variables are instance-variables,

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