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  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 private.

KEYWORDS

       scope, callback, namespace, public, protected, private

itcl                                                   3.0                                           code(3itcl)