Introduction
The ATLMacros sample demonstrates using the new ATL macros OBJECT_ENTRY_AUTO.
This replaces the BEGIN_OBJECT_MAP/OBJECT_ENTRY/END_OBJECT_MAP
combination.
The sample is based on the ATL Project created by the AppWizard. If you
choose to follow the steps in this document to create your own application, then
ensure that in the Application settings dialog you choose 'DLL project' and you
must ensure that you uncheck the 'Attributed' checkbox, otherwise the code will
be created using the new C++ Attributes for the COM classes.
In VC6 the Object Map BEGIN_OBJECT_MAP/END_OBJECT_MAP was used
to list all the ATL classes in the server that implemented COM classes. The
Object Map was located in the server .cpp file (where WinMain() or DllMain()
functions were located). To add a class to the map, the OBJECT_ENTRY
macro was used. Object Maps provides support for the registration,
initialization, and creation of a class.
In VC7 the OBJECT_ENTRY_AUTO macro is used for this instead.
Syntax:
OBJECT_ENTRY_AUTO(clsid, class )
Parameters:
clsid [in] |
The CLSID of a COM class implemented by the C++ class named class. |
class [in] |
The name of the C++ class implementing the COM class represented by
clsid. |
So now there is no Object Map. You simply place the object entry macros at
global scope in the project and it does all the work for you. The AppWizard puts
this macro to the end of the ATL class header file, so you have all your class
code in one place. Previously (VC6) it was easy to forget to add a class to the
Object Map. Now you have all your code in one place, so it is easy to reuse
existing classes since you can just copy the files that implement it and add
them to the project. No more messing around with OBJECT_ENTRY macros.
The Sample Application
The Math DLL implements two COM object: Adder and Subtracter.
The Adder object has a method Add that returns the sum of two addends passed
as parameters. A C++ class is implemented in Adder.h and Adder.cpp files.
Subtracter has a method Sub that returns the residual of the numbers passed
as parameters. A C++ class is implemented in Subtracter.h and Subtracter.cpp
files.
MathClient is a simple console application to test the Adder and Subtracter
objects. It reads two numbers and an operation sign (+/-) from the command line
and, depending on the operation, calls Adder or Subtracter. The operation is
performed and the results outputed
You must ensure that the Math.dll file has been registered for the
demonstration to work.
