As the itcl::class is a tcl command, you can insert code into the class declaration.
It is common C++ practice to have set/get methods to protect the variables in an object from manipulation outside the class.
This sample class creates a set of methods to set and enquire a list of protected variables.

  console show
  package require Itcl
  itcl::class tclas {
      foreach v "time distance" { 
        method get$v {} [subst -nocommands { return [subst $$v] }]
        method set$v nuval [subst -nocommands { set $v \$nuval } ]
        protected variable $v "Var $v"
      }
      constructor {} { puts "Constructs $this" }
      method speed {} { return [expr {[getdistance]/[gettime]}]}
  }
  tclas a
  a setdistance 2
  a settime 3.0
  puts "Travelled [a getdistance] taking Time [a gettime] so speed is [a speed]"

The variable list can be arbitrarily long of course when this would save considerable typing and validation effort.