DataBlade Developers Kit User's Guide Creating ActiveX Value Objects

To implement the client and server projects of an ActiveX value object, you add project-specific logic to particular C++ source files generated by BladeSmith.

This section contains the following subsections:

• The Generated Code, next
• Adding Project-Specific Logic to the Source Code
• Files to Edit
• ActiveX Properties
• Accessing Properties Using Visual Basic

The contents of the generated C++ source code differ from generated C source code (described in Chapter 5, Programming DataBlade Module Routines in C) in the following ways:

• Comments. BladeSmith includes comments to the developer regarding which sections must or may be modified; for more information, see Adding Project-Specific Logic to the Source Code.
• MI_FPARAM argument. This is not included in C++ code; it is a C language argument.
• Server connection handle. This handle is not needed for C++ code.
• Tracing. BladeSmith does not insert tracing logic into the generated C++ code. However, you can use the DataBlade API tracing macros in your server code; see Tracing and Error Handling for instructions.
• Error handling. BladeSmith inserts the DkErrorRaise() method into the generated routines to which you must add project-specific logic, naming the routine that has not been implemented and the file in which it resides (see Adding Project-Specific Logic to the Source Code). You can add DkErrorRaise() to other areas of the generated code and to your project-specific logic as appropriate. For information on the DkErrorRaise() object method, see Internal Object Methods.
• Utility functions. BladeSmith generates a C++ support library for each client and server project and uses the routines and methods of the library in its generated code. For information on this support library, see C++ Support Library.

For each routine in each support routine category that you specify for a particular opaque type, BladeSmith generates one of the following functions:

• The function definition and a function body that contains only a call to DkErrorRaise(). These routines are indicated by the comment Developer: TO DO.

You must supply project-specific internal logic to these routines.

BladeSmith inserts the DkErrorRaise() method into these routines, naming the routine that has not been implemented and the file in which it resides. When you supply the logic to these routines, you can remove the call to DkErrorRaise() or modify it to return an error more appropriate to the added logic. (For information on the DkErrorRaise() object method, see Internal Object Methods.)

• The function definition and a default function body. These routines are indicated by the comment Developer: Make changes in this section if necessary.

You can keep the default logic, or you can replace or modify it as appropriate for your project.

The following table lists each opaque type routine (by category and name), the source file where it is defined, and whether adding project-specific logic to that routine is required or optional.

For information on the usual behavior of the ActiveX custom methods (those defined in the OpaqueCommon.cpp and OpaqueCommon.h files), see Chapter 7, Using ActiveX Value Objects. For information on the default behavior of the server project routines, see Editing Opaque Type Support Routines in opaque.c.

If you choose to generate access methods in the BladeSmith New Opaque Type wizard, BladeSmith generates code to make the members of the data structure available as ActiveX properties so the client application developer can access those values.

If a member of an opaque type is an array, the following additional properties are made available:

• One-dimensional noncharacter array. A read-only property named NameDim is created to indicate the array dimension, and the property Name takes a one-based index as a parameter and returns the requested element.
• Two-dimensional noncharacter array. Properties named NameDim1 and NameDim2 are created, and the property Name takes a one-dimensional character array. Returns a string of type BSTR.
• Two-dimensional character array. Treated the same as a one-dimensional noncharacter array: NameDim indicates the dimension; the property Name takes a one-based index and returns the element.

This section describes how you can get and set ActiveX properties if you are using Visual Basic as your development environment.

For an ActiveX value object based on the opaque type named Opaque, with a non-array data structure member named x, you can get the corresponding property as follows:

member_value = Opaque.x

You can set the property as follows:

Opaque.x = member_value

If a data structure member is an array, you can get the property as follows: