Tcl method invocation functions

Description

The functions in this file are responsible for actually executing the messages sent to objects. They find out which method to call for a given object/message and call this method with the appropriate attributes. There are also routines that handle error reporting and debugging.

	Copyright (c) 1995 by softWorks.  All Rights Reserved.
	File:   method.c
	Author: Richard Schwaninger
	Date:   30/10/1995
	System: ithron.softworks.co.at
	RCS:    $Id: c_method.c,v 1.1 1996/08/30 08:48:44 /SW/app Exp /SW/app $

OO_ThatCmd - call some method in parent

Description

This function is responsible for calling a message in the parent context. It notes the current context of the object, finds the method corresponding to the given message in one of the parents and executes that message with the given arguments.

If more than one parent has a method for the given message then they are all executed (in an arbitrary order). If a TCL_ERROR or a TCL_BREAK code is returned from a call then this chaining is aborted and in the first case an error is returned.

This function implements the tcl command OO_That and in turn the call sequence $That msg ...

Here is an example:

	Method bla { a1 a2 } {
		$That bla $a1
		puts "$a2"
	}

Arguments

This command has the standard tcl call syntax.

Return Value

Returns a standard tcl result code and sets interp->result.

OO_EvalMethod - evaluate method command

Description

This function takes the given arguments, find's a method to call for the give message, builds up the corresponding tcl string and then evaluates this string. If an error happens then the corresponding error message is tried and called, otherwise the error is returned.

If the method cannot be found anywhere in the inheritance chain then the Unknown message is sent to the current object (if that does not exist too then an error happens).

Just before and just after the method invocation the object debugger entry is called (if enabled) so we can check and modify arguments.

Arguments.

interp: Pointer to current interpreter
Class: Name of class for the current object
This: Object name for the current object
Msg: The message signature that was sent to the current object
argc: number of arguments for this message
argv: list of actual arguments for this message

Return Value

This function returns a Tcl_Result-code, either obtained by calling OO_Eval() or from the method lookup. It returns TCL_BREAK to signify something special, but I don't know what.

OO_EvalMethodCmd - method evaluator

Description

This routine is the procedure visible in the tcl interpreter. It does some simple housekeeping and allows for debugging before calling the main evaluator routine OO_EvalMethod.

Arguments

This command has the standard tcl call syntax

Return Value

The function returns either TCL_OK or TCL_ERROR to indicate success or failure of the call.