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