scope(n) [redhat man page]

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 varName 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 vari-
       ables 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 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)

code(n) 							    [incr Tcl]								   code(n)

__________________________________________________________________________________________________________________________________________________

NAME

       code - capture the namespace context for a code fragment

SYNOPSIS

       itcl::code ?-namespace name? command ?arg arg ...?
_________________________________________________________________

DESCRIPTION

       Creates	a  scoped  value  for  the specified command and its associated arg arguments.	A scoped value is a list with three elements:  the
       "@scope" keyword, a namespace context, and a value string.  For example, the command
	      namespace foo {
		  code puts "Hello World!"
	      }
       produces the scoped value:
	      @scope ::foo {puts {Hello World!}}
       Note that the code command captures the current namespace context.  If the -namespace flag  is  specified,  then  the  current  context	is
       ignored, and the name string is used as the namespace context.

       Extensions  like  Tk  execute  ordinary	code fragments in the global namespace.  A scoped value captures a code fragment together with its
       namespace context in a way that allows it to be executed properly later.  It is needed, for example, to wrap up code fragments  when  a	Tk
       widget is used within a namespace:
	      namespace foo {
		  private proc report {mesg} {
		      puts "click: $mesg"
		  }

		  button .b1 -text "Push Me"	     -command [code report "Hello World!"]
		  pack .b1
	      }
       The  code  fragment  associated with button .b1 only makes sense in the context of namespace "foo".  Furthermore, the "report" procedure is
       private, and can only be accessed within that namespace.  The code command wraps up the code fragment in a way that allows it  to  be  exe-
       cuted properly when the button is pressed.

       Also,  note  that  the  code command preserves the integrity of arguments on the command line.  This makes it a natural replacement for the
       list command, which is often used to format Tcl code fragments.	In other words, instead of using the list command like this:
	      after 1000 [list puts "Hello $name!"]
       use the code command like this:
	      after 1000 [code puts "Hello $name!"]
       This not only formats the command correctly, but also captures its namespace context.

       Scoped commands can be invoked like ordinary code fragments, with or without the eval command.  For example, the following statements  work
       properly:
	      set cmd {@scope ::foo .b1}
	      $cmd configure -background red

	      set opts {-bg blue -fg white}
	      eval $cmd configure $opts
       Note that scoped commands by-pass the usual protection mechanisms; the command:
	      @scope ::foo {report {Hello World!}}
       can be used to access the "foo::report" proc from any namespace context, even though it is private.

KEYWORDS

       scope, callback, namespace, public, protected, private

itcl									3.0								   code(n)