configbody tcl tk

package require Itcl

itcl::class sampleconf { ;# a sample class with a single public variable
    public variable publicv ;# this var is adjusted using the configure -publicv...
    constructor {} { }
    method setpublicv {dn} {
       set publicv "$dn"
       puts $dn
     }
    method shwopublicv {} {
       puts $publicv
     }
  }

# create a sample instance of the class:
set btn [sampleconf  h2]

# directory configure in the class
h2 configure -publicv "good"
h2 shwopublicv

# add a widiget configure for a variable
# add a configbody for public variable  publicv
itcl::configbody sampleconf::publicv  {tk_messageBox -message "Publicv in $this was set to $publicv by a configure command."}

h2 configure -publicv "A new Value"

# change the publicv by configure and you see a message box.

h2 configure -publicv "The same old Value"

h2 setpublicv "A value which is not sent via the configbody"

# change the publicv again by configure and again you see a message box.
h2 configure -publicv "Another Value"