NAME

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

SYNOPSIS

       itcl::configbody className::varName body
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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 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.
              itcl::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 {}
              }

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

              itcl::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]"
              }
              itcl::delete object x

KEYWORDS

       class, object, variable, configure