NAME
body - change the body for a class method/proc
SYNOPSIS
body className::function args body
_________________________________________________________________
DESCRIPTION
The body command is used outside of an [incr Tcl] 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 class command with declarations
for methods, procs, instance variables and common vari
ables. 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::function" identifies the method/proc
being changed.
If an args list was specified when the function was
defined in the class definition, the args list for the
body 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 argu
ments. The special args argument acts as a wildcard when
included in the args list in the class definition; it will
match zero or more arguments of any type when the body is
redefined.
If the body string starts with "@", it is treated as the
symbolic name for a C procedure. The args 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 body does not start with
"@", it is treated as a Tcl command script. When the
function is invoked, command line arguments are matched
against the args list, and local variables are created to
represent each argument. This is the usual behavior for a
Tcl-style proc.
Symbolic names for C procedures are established by regis
tering procedures via Itcl_RegisterC(). This is usually
done in the Tcl_AppInit() procedure, which is automati
cally called when the interpreter starts up. In the
with the symbolic name "foo". This procedure can be ref
erenced in the body 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. The method bodies are included
below the class definition via the body command. Note
that the bodies of the constructor/destructor must be
included in the class definition, but they can be rede
fined via the body command as well.
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
KEYWORDS
class, object, procedure
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