Objective:

This Article describes the methodology of creating a CAA V5 object that can be accessed from scripting languages. The step by step procedure of creating a CAA V5 object( in Visual Studio 2005 ) and accessing the same from VBA (CATIA) is also presented.

Description:

·         For calling any CAA V5 object from simple scripting language we need to use automation interfaces. Automation Interfaces are special interfaces that allow CAA V5 programming from simple scripting languages.

• The CAA V5 IDL (Interface Definition Language) is the language used to write automation interfaces.
• The CAA V5 IDL (Interface Definition Language) is dedicated to create programming language independent interfaces that we can use from both a compiled languages such as C++, and scripting languages such as Visual Basic and JScript with Windows, and Basic Script with UNIX.
• IDL provides C-language like declarations that associate an identifier with a type.
• The IDL compiler (MIDL) builds the run time type library from IDL source files and stores it in a shared library(Type Library or .tplib).
• Scripting languages uses these type libraries (.tplib) to access the type information about the functions. Actual function implementation is available in  a DLL.
• The type library is a compiled version of a set of IDL files. It contains the description of all the interfaces, all the method prototypes, properties, and all the parameters they require along with their types.
• The base interface for exposed interfaces that are used in scripting languages is IDispatch interface. IDispatch interface derives from IUnknown interface.
• Compared to C++, scripting languages have parameter type support restrictions. The compatible parameters of the method signatures are available in the CAA Encyclopedia at the following link.

CAADoc\Doc\online\CAASysTechArticles\CAASysAutomationItf.htm

Fig 1. Schematic Diagram showing how a  VBA application access CAA Component.