configbody(n) [incr Tcl] configbody(n) ______________________________________________________________________________
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 defini-
tion 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 rede-
fine 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 vari-
ables 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 sym-
bolic name for a C procedure. Otherwise, it is treated as a Tcl com-
mand script.
Symbolic names for C procedures are established by registering proce-
dures 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
itcl 3.0 configbody(n)
Mac OS X 10.8 - Generated Wed Sep 5 16:32:28 CDT 2012