configbody(n)							    [incr Tcl]							     configbody(n)

NAME

       configbody - change the "config" code for a public variable

SYNOPSIS

       configbody className::varName body

DESCRIPTION

       The  configbody	command  is  used outside of an [incr Tcl] class definition to define or redefine the configuration code associated with a
       public variable.  Public variables act like configuration options for an object.  They can be modified outside the class  scope	using  the
       built-in  configure  method.  Each variable can have a bit of "config" code associate with it that is automatically executed when the vari-
       able is configured.  The configbody command can be used to define or redefine this body of code.

       Like the body command, this facility allows a class definition to have separate "interface" and "implementation"  parts.   The  "interface"
       part  is  a  class  command  with declarations for methods, procs, instance variables and common variables.  The "implementation" part is a
       series of body and configbody commands.	If the "implementation" part is kept in a separate file, it can be sourced again and again as bugs
       are  fixed,  to support interactive development.  When using the "tcl" mode in the emacs editor, the "interface" and "implementation" parts
       can be kept in the same file; as bugs are fixed, individual bodies can be highlighted and sent to the test application.

       The name "className::varName" identifies the public variable being updated.  If the body string starts with "@", it is treated as the  sym-
       bolic name for a C procedure.  Otherwise, it is treated as a Tcl command script.

       Symbolic  names for C procedures are established by registering procedures via Itcl_RegisterC().  This is usually done in the Tcl_AppInit()
       procedure, which is automatically called when the interpreter starts up.  In the following example, the procedure My_FooCmd() is registered
       with the symbolic name "foo".  This procedure can be referenced in the configbody command as "@foo".  int Tcl_AppInit(interp)
	   Tcl_Interp *interp;	   /* Interpreter for application. */ {
	   if (Itcl_Init(interp) == TCL_ERROR) {
	       return TCL_ERROR;
	   }

	   if (Itcl_RegisterC(interp, "foo", My_FooCmd) != TCL_OK) {
	       return TCL_ERROR;
	   } }

EXAMPLE

       In  the following example, a "File" class is defined to represent open files.  Whenever the "-name" option is configured, the existing file
       is closed, and a new file is opened.  Note that the "config" code for a public variable is optional.  The "-access"  option,  for  example,
       does not have it.  class File {
	   private variable fid ""

	   public variable name ""
	   public variable access "r"

	   constructor {args} {
	       eval configure $args
	   }
	   destructor {
	       if {$fid != ""} {
		   close $fid
	       }
	   }

	   method get {}
	   method put {line}
	   method eof {} }

       body File::get {} {
	   return [gets $fid] } body File::put {line} {
	   puts $fid $line } body File::eof {} {
	   return [::eof $fid] }

       configbody File::name {
	   if {$fid != ""} {
	       close $fid
	   }
	   set fid [open $name $access] }

       # # See the File class in action: # File x

       x configure -name /etc/passwd while {![x eof]} {
	   puts "=> [x get]" } delete object x

KEYWORDS

       class, object, variable, configure

itcl									3.0							     configbody(n)