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markom |
'\"
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'\" Copyright (c) 1993-1998 Lucent Technologies, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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'\" RCS: $Id: body.n,v 1.1.1.1 2002-01-16 10:24:46 markom Exp $
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'\"
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.so man.macros
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.TH body n 3.0 itcl "[incr\ Tcl]"
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.BS
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'\" Note: do not modify the .SH NAME line immediately below!
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.SH NAME
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body \- change the body for a class method/proc
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.SH SYNOPSIS
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\fBbody \fIclassName\fB::\fIfunction args body\fR
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.BE
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.SH DESCRIPTION
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.PP
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The \fBbody\fR command is used outside of an \fB[incr\ Tcl]\fR
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class definition to define or redefine the body of a class
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method or proc. This facility allows a class definition
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to have separate "interface" and "implementation" parts.
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The "interface" part is a \fBclass\fR command with declarations
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for methods, procs, instance variables and common variables.
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The "implementation" part is a series of \fBbody\fR and
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\fBconfigbody\fR commands. If the "implementation" part
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is kept in a separate file, it can be sourced again and
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again as bugs are fixed, to support interactive development.
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When using the "tcl" mode in the \fBemacs\fR editor, the
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"interface" and "implementation" parts can be kept in the
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same file; as bugs are fixed, individual bodies can be
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highlighted and sent to the test application.
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.PP
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The name "\fIclassName\fB::\fIfunction\fR"
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identifies the method/proc being changed.
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.PP
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If an \fIargs\fR list was specified when the \fIfunction\fR was
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defined in the class definition, the \fIargs\fR list for the
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\fBbody\fR command must match in meaning. Variable names
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can change, but the argument lists must have the same required
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arguments and the same default values for optional arguments.
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The special \fBargs\fR argument acts as a wildcard when included
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in the \fIargs\fR list in the class definition; it will match
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zero or more arguments of any type when the body is redefined.
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.PP
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If the \fIbody\fR string starts with "\fB@\fR", it is treated
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as the symbolic name for a C procedure. The \fIargs\fR list
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has little meaning for the C procedure, except to document
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the expected usage. (The C procedure is not guaranteed to
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use arguments in this manner.) If \fIbody\fR does not start
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with "\fB@\fR", it is treated as a Tcl command script. When
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the function is invoked, command line arguments are matched
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against the \fIargs\fR list, and local variables are created
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to represent each argument. This is the usual behavior for
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a Tcl-style proc.
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.PP
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Symbolic names for C procedures are established by registering
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procedures via \fBItcl_RegisterC()\fR. This is usually done
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in the \fBTcl_AppInit()\fR procedure, which is automatically called
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when the interpreter starts up. In the following example,
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the procedure \fCMy_FooCmd()\fR is registered with the
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symbolic name "foo". This procedure can be referenced in
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the \fBbody\fR command as "\fC@foo\fR".
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.CS
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int
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Tcl_AppInit(interp)
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Tcl_Interp *interp; /* Interpreter for application. */
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{
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if (Itcl_Init(interp) == TCL_ERROR) {
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return TCL_ERROR;
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}
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if (Itcl_RegisterC(interp, "foo", My_FooCmd) != TCL_OK) {
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return TCL_ERROR;
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}
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}
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.CE
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.SH EXAMPLE
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In the following example, a "File" class is defined to represent
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open files. The method bodies are included below the class
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definition via the \fBbody\fR command. Note that the bodies
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of the constructor/destructor must be included in the class
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definition, but they can be redefined via the \fBbody\fR command
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as well.
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.CS
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class File {
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private variable fid ""
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constructor {name access} {
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set fid [open $name $access]
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}
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destructor {
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close $fid
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}
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method get {}
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method put {line}
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method eof {}
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}
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body File::get {} {
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return [gets $fid]
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}
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body File::put {line} {
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puts $fid $line
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}
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body File::eof {} {
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return [::eof $fid]
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}
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#
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# See the File class in action:
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#
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File x /etc/passwd "r"
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while {![x eof]} {
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puts "=> [x get]"
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}
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delete object x
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.CE
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.SH KEYWORDS
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class, object, procedure
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