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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  exe-cuted executed
       cuted when the variable 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 symbolic 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)