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scope(n)                                         [incr Tcl]                                         scope(n)



NAME
       scope - capture the namespace context for a variable

SYNOPSIS
       scope name


DESCRIPTION
       Creates  a  scoped  value  for  the specified name, which must be a variable name.  If the name is an
       instance variable, then the scope command returns a string of the following form: @itcl  object  var-Name varName
       Name  This is recognized in any context as an instance variable belonging to object.  So with itcl3.0
       and beyond, it is possible to use instance variables in conjunction with widgets.   For  example,  if
       you have an object with a private variable x, and you can use x in conjunction with the -textvariable
       option of an entry widget.  Before itcl3.0, only common variables could be used in this manner.

       If the name is not an instance variable, then it must be a common variable or a global variable.   In
       that case, the scope command returns the fully qualified name of the variable, e.g., ::foo::bar::x.

       If the name is not recognized as a variable, the scope command returns an error.

       Ordinary  variable names refer to variables in the global namespace.  A scoped value captures a vari-able variable
       able name together with its namespace context in a way that  allows  it  to  be  referenced  properly
       later.  It is needed, for example, to wrap up variable names when a Tk widget is used within a names-pace: namespace:
       pace: namespace foo {
           private variable mode 1

           radiobutton .rb1 -text "Mode #1"         -variable [scope mode] -value 1
           pack .rb1

           radiobutton .rb2 -text "Mode #2"         -variable [scope mode] -value 2
           pack .rb2 } Radiobuttons .rb1 and .rb2 interact via the variable "mode" contained in  the  names-pace namespace
       pace  "foo".   The  scope  command  guarantees  this  by  returning the fully qualified variable name
       ::foo::mode.

       You should never use the @itcl syntax directly.  For example, it is a bad idea  to  write  code  like
       this:  set  {@itcl  ::fred  x}  3 puts "value = ${@itcl ::fred x}" Instead, you should always use the
       scope command to generate the variable name dynamically.  Then, you can pass that name to a widget or
       to any other bit of code in your program.


KEYWORDS
       code, namespace, variable



itcl                                                                                                scope(n)