'\"
'\" Copyright (c) 1993-1998  Lucent Technologies, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" RCS: $Id: body.n,v 1.1.1.1 2005/03/01 06:52:42 chenyu Exp $
'\"
.so man.macros
.TH body n 3.0 itcl "[incr\ Tcl]"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
body \- change the body for a class method/proc
.SH SYNOPSIS
\fBbody \fIclassName\fB::\fIfunction args body\fR
.BE

.SH DESCRIPTION
.PP
The \fBbody\fR command is used outside of an \fB[incr\ Tcl]\fR
class definition to define or redefine the body of a class
method or proc.  This facility allows a class definition
to have separate "interface" and "implementation" parts.
The "interface" part is a \fBclass\fR command with declarations
for methods, procs, instance variables and common variables.
The "implementation" part is a series of \fBbody\fR and
\fBconfigbody\fR 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 \fBemacs\fR 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.
.PP
The name "\fIclassName\fB::\fIfunction\fR"
identifies the method/proc being changed.
.PP
If an \fIargs\fR list was specified when the \fIfunction\fR was
defined in the class definition, the \fIargs\fR list for the
\fBbody\fR command must match in meaning.  Variable names
can change, but the argument lists must have the same required
arguments and the same default values for optional arguments.
The special \fBargs\fR argument acts as a wildcard when included
in the \fIargs\fR list in the class definition; it will match
zero or more arguments of any type when the body is redefined.
.PP
If the \fIbody\fR string starts with "\fB@\fR", it is treated
as the symbolic name for a C procedure.  The \fIargs\fR list
has little meaning for the C procedure, except to document
the expected usage.  (The C procedure is not guaranteed to
use arguments in this manner.)  If \fIbody\fR does not start
with "\fB@\fR", it is treated as a Tcl command script.  When
the function is invoked, command line arguments are matched
against the \fIargs\fR list, and local variables are created
to represent each argument.  This is the usual behavior for
a Tcl-style proc.
.PP
Symbolic names for C procedures are established by registering
procedures via \fBItcl_RegisterC()\fR.  This is usually done
in the \fBTcl_AppInit()\fR procedure, which is automatically called
when the interpreter starts up.  In the following example,
the procedure \fCMy_FooCmd()\fR is registered with the
symbolic name "foo".  This procedure can be referenced in
the \fBbody\fR command as "\fC@foo\fR".
.CS
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;
    }
}
.CE

.SH EXAMPLE
In the following example, a "File" class is defined to represent
open files.  The method bodies are included below the class
definition via the \fBbody\fR command.  Note that the bodies
of the constructor/destructor must be included in the class
definition, but they can be redefined via the \fBbody\fR command
as well.
.CS
class File {
    private variable fid ""
    constructor {name access} {
        set fid [open $name $access]
    }
    destructor {
        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]
}

#
# See the File class in action:
#
File x /etc/passwd "r"
while {![x eof]} {
    puts "=> [x get]"
}
delete object x
.CE

.SH KEYWORDS
class, object, procedure
