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



NAME
       code - capture the namespace context for a code fragment

SYNOPSIS
       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 names-pace: namespace:
       pace: 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 names-pace namespace
       pace  "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  prop-erly properly
       erly 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  frag-ments. fragments.
       ments.   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  for-mats formats
       mats 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  -back-ground -background
       ground 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)