NAME¶
body - change the body for a class method/proc
SYNOPSIS¶
itcl::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
"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 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 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
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.
itcl::class File {
private variable fid ""
constructor {name access} {
set fid [open $name $access]
}
destructor {
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]
}
#
# See the File class in action:
#
File x /etc/passwd "r"
while {![x eof]} {
puts "=> [x get]"
}
itcl::delete object x
KEYWORDS¶
class, object, procedure