NAME

       itcl::code - capture the namespace context for a code fragment

SYNOPSIS

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