itcl User Commands - body
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 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 "imple-
mentation" 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 arguments. 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 register-
ing 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 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 redefined 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