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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: configbody.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 configbody 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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configbody \- change the "config" code for a public variable
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.SH SYNOPSIS
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\fBconfigbody \fIclassName\fB::\fIvarName body\fR
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.BE
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.SH DESCRIPTION
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.PP
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The \fBconfigbody\fR command is used outside of an \fB[incr\ Tcl]\fR
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class definition to define or redefine the configuration code
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associated with a public variable. Public variables act like
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configuration options for an object. They can be modified
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outside the class scope using the built-in \fBconfigure\fR method.
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Each variable can have a bit of "config" code associate with it
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that is automatically executed when the variable is configured.
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The \fBconfigbody\fR command can be used to define or redefine
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this body of code.
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.PP
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Like the \fBbody\fR command, 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::\fIvarName\fR"
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identifies the public variable being updated.
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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. Otherwise, it is
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treated as a Tcl command script.
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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 \fBconfigbody\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. Whenever the "-name" option is configured, the
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existing file is closed, and a new file is opened. Note that
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the "config" code for a public variable is optional. The "-access"
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option, for example, does not have it.
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.CS
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class File {
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private variable fid ""
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public variable name ""
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public variable access "r"
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constructor {args} {
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eval configure $args
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}
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destructor {
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if {$fid != ""} {
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close $fid
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}
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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 $fid]
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}
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configbody File::name {
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if {$fid != ""} {
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close $fid
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}
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set fid [open $name $access]
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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
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x configure -name /etc/passwd
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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, variable, configure
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