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 defini-
       tion 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 variable
       is  configured.   The configbody command can be used to define or rede-
       fine 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 vari-
       ables  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 com-
       mand script.

       Symbolic names for C procedures are established by  registering  proce-
       dures  via ItclRegisterC().  This is usually done in the TclAppInit()
       procedure, which is automatically called when  the  interpreter  starts
       up.   In the following example, the procedure MyFooCmd() is registered
       with the symbolic name "foo".  This procedure can be referenced in  the
       configbody command as "@foo".  int TclAppInit(interp)
           TclInterp *interp;     /* Interpreter for application. */ {
           if (ItclInit(interp) == TCLEROR) {
               return TCLEROR;
           }

           if (ItclRegisterC(interp, "foo", MyFooCmd) != TCLOK) {
               return TCLEROR;
           } }


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)