---
name: "configbody"
section: "n"
platform: "macos"
package: "tcl"
version: "152"
release: "macOS 26.5"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/configbody/n"
---

# configbody(n)

change the "config" code for a public variable

## NAME

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

## SYNOPSIS

**itcl::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 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