How to create an enum and callback function

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Introduction

Have you ever seen functions by name EnumFunctions? Like EnumWindows etc. Have you ever wondered how they are created? In this article, we will create a simple one! Just be relaxed and read this article to EOF!

What is an enum function?

These types of functions are ...!?! Let me explain like this: assume that you have some fruits. OK? Some apples, oranges, and bananas. You are searching for apples. And, for each apple you can find, you will shout: "Hey I found another apple!" This is the role of this type of functions: for each element, return something.

Let's start

Declaring an EnumFunction is simple. First, you should have a variable type to tell the function what kind of function is the input. See this code snippet (declarations in the header file):

typedef BOOL (CALLBACK*YOURPROCTYPE)(FirstType,SecondType,...);

Now see mine:

typedef BOOL (CALLBACK*MYPROC)(LPCTSTR);

And for declaring the EnumFunction:

ReturnType WINAPI EnumFunction(YOURPROCTYPE lpProcname,arg-list,…);

And mine:

BOOL WINAPI EnumFunc(MYPROC lpProc);

EnumFunc passes the parameters to a callback function:

ReturnType CALLBACK yourProcName(FirstType,SecondType,...);

Note that the argument list of this callback function must be what you give in YOURPROCTYPE:

BOOL CALLBACK MyProc (LPCTSTR prompt);

Here are my sample code declarations:

typedef BOOL (CALLBACK*FILESPROC)(LPCTSTR);
void WINAPI EnumFiles(FILESPROC lpEnumFiles,LPCTSTR lpszFileName);
int CALLBACK EnumFilesProc (LPCTSTR lpszFileName);

And here goes the EnumFiles function. Its task is to find the files in the given path, and for each file, calls the callback function:

void WINAPI EnumFiles(FILESPROC lpEnumFiles,LPCTSTR lpszFileName)
{
        CString nfle;
        numoffiles=0;
        CFileFind file;
        BOOL bFind=file.FindFile(lpszFileName,NULL);//Find first file in the given
        //path
        while (bFind)//While bFind==True continue finding...
        {
               bFind=file.FindNextFile(); //Find next file
               numoffiles=lpEnumFiles(file.GetFileName());//Call given callback function
               //by user with appropriate inputs 
        }
        nfle.Format("%d  Files found",numoffiles);
        AfxMessageBox(nfle);//Give the user number of files found in
        //the given path
}

BOOL CALLBACK EnumFilesProc(LPCTSTR lpszFileName)
{ 
        numoffiles++;
        list->InsertString(list->GetCount(),lpszFileName); 
        return numoffiles;
}

Now for calling the EunmFunction, you only need to write some code:

list->ResetContent();
EnumFiles(EnumFilesProc,"C:\\*.exe");

In this source code, we will get a path and enumerate all the files in the path! I use this enumeration technique to get all the sections in an INI file, and you can do anything you want! Any opinions and comments are welcome. Or questions maybe..