Tuesday

Components of ObjectARX applications.

6 Comments Nov-28-2006 | Posted by M. Mazhar Basa | Printable Version | Level |

Hello everyone,

In this article I will introduce the components of ObjectARX™ applications and tools required to develop them (Fig.1). I know, it looks scary. But it gives you amazing customization abilities.

Fig.1 Components of an ObjectARX project

As I mentioned in my previous article, ObjectARX™ applications are “.dll” files. Of course, there may be other files like “.xls”, “.doc”, “.exe”, “.bmp” ect… or other resource files written in other programming languages, “.php”, “.asp” files, database, hardware driver connections, etc… depending on what your ObjectARX™ project includes. You should consider it a project composed of many components and files, rather than a code snippet that can be copy-pasted as part of a macro.

This “.dll” file, has “.ARX”, or “.DBX” extension. The main application, which I mentioned above, must be ARX file; however if you create your custom objects, which are derived from AutoCAD objects classes, these classes are stored in a DBX extension file, which is linked to main ARX file. At the starting it becomes scary, why two different files, not one? This idea arises from the separation of UI (user interface) from database operations.

ARX file

In this file you keep the code related to the user interface like toolbars, MFC (Microsoft Foundation Classes, which is the standard dialog boxes, buttons, scroll bars etc. that Microsoft use in Windows applications), AutoCAD commands that your application handle (just like the standard commands you enter from the command line), and other code that organize the general operation of you application.

DBX file

In this file, you keep your own “custom classes”. Those who don’t know what “object-oriented programming” is, should skip this part, unless they want to discover a new way of programming. Those who know about it should also skip because I will try to explain it  As I mentioned in my previous article, one of the most exciting features of ObjectARX programming is ability to create your own custom objects, which may be related to the concept of “object-oriented programming” in AutoCAD. I will try to explain with an example. As it is mentioned in this article, TABLE command is introduced with AutoCAD 2005®. This table entity is a custom object derived from several line, and text entities combined together to form a TABLE object. I am sure that most of the ObjectARX™ programmers have already created their TABLE objects before AutoCAD 2005®, and used it in their own applications. At least, I have done that. These DBX files or the custom objects inside them are totally reusable, and customizable. Once you create one custom object, you can use it in different applications or you can derive new custom objects from them and adapt them to your new problem.

C++ Compiler

Compiler, is a program which compiles the code into and “.exe” or “.dll” file. Thus, we will use a separate program to write our code. Here is a table for C++ compilers for AutoCAD and C++ versions. Sorry for users of versions before 2000, I started with R14

ARXWizard

It is included in ObjectARX™ SDK (Software Development Kit), which can be downloaded from www.objectarx.com for different versions of AutoCAD. This wizard enables us to create our ObjectARX™ projects, files and objects from default templates and add/modify commands (to AutoCAD) that our application will handle. It is nearly impossible to create a working project for a newbie without ARXWizard. When you install it, it adds a toolbar inside VS2002 and adds itself to the other wizards of VS.

AutoCAD Libraries

They are also included in SDK. They are inside /inc and /lib folders. Actually, you do not need to deal with these files personally. You just enter these directories into your project settings and compiler. As I mentioned in my previous article, the main idea of ObjectARX™ programming is using AutoCAD’s own source code, but not limited to it, which is composed of these libraries. These libraries include AutoCAD’s own object classes and global functions (like shortcut functions to database related works; angle, distance measurement functions and much more…). 

MFC (Microsoft Foundation Classes) Libraries

Libraries to use standard Microsoft dialog boxes, buttons etc… Note that, even if you can use your external resources and MFC libraries, AutoCAD libraries also include objects derived from MFC.

COM+ (Component Object Model) Connections

For those who used a VBA macro or any other program that enables AutoCAD to communicate with other programs (like EXCEL), has already used COM without noticing it. COM is an intermediate platform which enables different programs (even written in different programming languages) to communicate with each other.

Your own Libraries

You can use your own libraries or any other library that is created with C++ or any other programming language.

Web Server Connections

For now it’s just my imagination; who needs to include a web server inside an ObjectARX™ application? However, with the development of internet, it enters every field. It is possible to implement some PHP, ASP, JAVA, AJAX whatever web language you want, through an ObjectARX™ application, will run on a server and work as a part of your project.

As you see, I am just trying to enlarge your imagination, because there are no limits for the components that can be added to an ObjectARX™ application. Those I mentioned are only limited to my programming experiences, for more experienced and talented programmers there may be much more…

Thanks for reading, and please stay tuned. In my next article, for those who are willing to write their first program, I will explain the installation of basic components (Fig.1) for an Object ARX application, so that shortly we can write our first “Hello World” program