Getting started with COM programming 1- creating projects and writing interfaces

The following projects were built and developed using vs2010, And vs2015、2017 Not much difference

1、 establish ATL Project and name it test1

2、 Application type selection Dynamic link library

 3、 Right click item properties Add the class And select ATL Simple objects , Name it Func

 

4、 Select a custom interface

 

5、 Press Ctrl+Shift+C Switch to Class view , Right click IFunc Class and add methods , Let's write one Interface for integer summation Add

The interface has three parameters in total ,[in LONG n1,in LONG n2,out retval LONG* pRet]

among pRet Is the return value , Yes, it will n1 and n2 The result of summation , With LONG A pointer to is passed into the function as an argument

6、 After creating the interface , Click... In class view mode CFunc class , Click again Add Interface , Jump to the implementation of the interface , Modify the interface implementation

 7、 Realization Cat Interface （ String splicing interface , Reference resources Add Interface creation ）

There are three parameters [in BSTR str1,in BSTR str2,out retval BSTR* pRet]

And Add As the interface , The third parameter is the result of the splicing of the first two parameters

8、 Compile and pass （ If not compiled , It may be registration COM Failure , You need an administrator to run visual studio Compile later ）, Next we will talk about How to call your own COM Interface