Classes

Contents

• Classes
  • Introduction
  • Types
  • Classes
  • Objects
  • Interfaces
  • Categories

Introduction

This page contains basic information for coders on Types and Classes.

Types

In SOZ, a Type is just another name for a Class.

There are three main distinctions between types:

• Values - which return a Value as their result
• Objects - which return an ID of an object as their result.
• Scripts - which just are run for their internal results.

SZOBBase is the base type for all of SOZ-LIVE.

The Base hierarchy of Types for the Project is:

• SZOBBase - Abstract Base class.
  • Lisp - Abstract Lisp Value Class
  • SZOBObject - Abstract Object Class
  • SZOBScript - Abstract Script Class

The full hierarchy of SOZ-LIVE is listed here.
Each entry is a link to the documentation for the particular class.

Classes

All classes are derived from the Base Class - SZOBBase.

While SOZ only uses single inheritance:

• Classes can share an interface with other classes.
• Classes can be contained in multiple Categories.

A class is defined with a call to register it in the Meta Environment using the Class Make function:

(SZMAClass-make "SZGECurve" "SZGELine" :vlax-false "Line Geometry Class")

Where the SZMAClass-Make function has the following signature:

(SZMAClass-make BaseClass ClassName isAbstract? Description)

And:

Item	Type	Description
BaseClass	String	Name of the Base class for the Class
ClassName	String	Name of the Class being created
isAbstract?	Boolean	is the Class an Abstract Class
Description	Comment	a Description of the Class being created

Note:
- Many of the specified classes are Abstract classes - meaning that they can’t be instanced / objects created from them.
- They are used to set out the hierarchy in a logical fashion so that LSP works for each type / class specified.

Objects

All Objects are made using the Make method of the Class, as shown below:

(SZMAMethod-make "SZGELine" "Make" (list "POINT0" "POINT1") (list "SZGEPoint" "SZGEPoint") "SZGELine" "Make a Line")
(defun SZGELine-make ( POINT0 POINT1 ) (SZOBObject-Maker "SZGELine" )) 

This differs to other Lisp OO implementations where a make routine for a Line class would be named make-line.

The Make arguments are stored on the Object or Entity in an Alist, together with the Class of the Object. They contain all the information required to Make, Edit and Update the object as and if required.

Interfaces

An Interface enables a class A to be used where class B would be required, as it contains the same method signatures as Class B.

(SZMAInterface-make "AcDbPoint" (list "SZGEPoint" "Point"))

This then enables an AcDbPoint entity to be used interchangeably with either a SZGEPoint object or a Point value.

Where SZMAInterface-make has the following signature:

(SZMAInterface-make ClassName Classes)

And:

Item	Type	Description
ClassName	String	Name of the Class
Classes	List:ClassName	a list of Classes to Interface with

Categories

A Category can be considered an orthogonal concept to a Class.

Both have a hierarchy, and both only allow single inheritance within.

However, a Class may be a member of multiple Categories, eg:

(SZMAClass-addCategories "Name" "SZCEPart-PipeRun" (list "Mechanical" "Piping"))

where SZMAClass-addCategories has the following signature:

(SZMAClass-addCategories Type ClassName Categories)

And:

Item	Type	Description
Type	String	The type of the category
ClassName	String	Name of the Class
Categories	List:Category	a list of Category Names for the Class

For the full list - refer to the Categories document.

Note:
- Each Category has a corresponding M- (Make) command that can be entered at the command line.
- This resolves class naming issues as the class name can be all about functionality.