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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 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 com-
       mand.  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)
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