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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  cur-
       rent  context  is ignored, and the name string is used as the namespace
       context.

       Extensions like Tk execute ordinary code	fragments in the global	 name-
       space.  A scoped	value captures a code fragment together	with its name-
       space 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 executed 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  pri-
       vate.

KEYWORDS
       scope, callback,	namespace, public, protected, private

itcl				      3.0			       code(n)

NAME | SYNOPSIS | DESCRIPTION | KEYWORDS

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