NAME

       itcl::scope - capture the namespace context for a variable

SYNOPSIS

       itcl::scope name
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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 name which will resolve in any context as an instance variable
       belonging  to  object.   The  precise  format  of this name is an internal detail to Itcl.  Use of such a
       scoped value makes it 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  variable
       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 namespace:
              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 namespace "foo".  The  scope
       command guarantees this by returning the fully qualified variable name ::foo::mode.

       You  should  never attempt to craft your own scoped variable names, even if you believe you've flawlessly
       reverse-engineered the encoding.  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(3itcl)