2014-11-03 58 views
1

我有一个C++函数,我在Excel 2013通过与VC2013内置一个DLL使用:如何通过DLL函数的参数将变量返回给Excel?

double my_function(double input) { 
//do something 
return input*input; 
} 

在Excel VBA我有这个功能是这样的:

Declare Function my_function Lib "DLL_with_my_function.dll" (ByVal input As Double) As Double 

这种运作良好,到目前为止,但是,现在,我希望能够通过第二个参数返回第二条信息,说错误代码。理想情况下,此错误代码可以输出到Excel中的单元格,或者至少通过debug.print输出到控制台。我被困在使整个事情工作,并有多次Excel崩溃。这是我徒劳的尝试:

double my_function(double input, long *error_code) { 
*error_code = 5; 
return input*input; 
} 

#in Excel:  
Declare Function my_function Lib "DLL_with_my_function.dll" (ByVal input As Double, ByRef error_code as long) As Double 

当我打电话从工作表中的功能和指示细胞作为第二个参数的Excel崩溃我。什么是正确的,优雅的方式来做到这一点?

回答

1

你只是不能给EXEL细胞只要数到C \ C++,因为它不会自动转换

你可以这样做:

double my_function(double input, long *error_code) { 
    *error_code = 5; 
    return input*input; 
} 
//unless you don't want to build the long from bytes, you can use function to do so. 
long get_error_code(long* error_code){ 
    return *error_code; 
} 

在Excel中宣布新的功能太:

Declare Function my_function Lib "DLL_with_my_function.dll" (ByVal input As Double, ByVal error_code as long) As Double 
Declare Function get_error_code Lib "DLL_with_my_function.dll" (ByVal error_code as long) As Long 

#now in the function you should allocate memory to the error code: 
Dim hMem As Long, pMem As Long 
#hMem is handle to memory not a pointer 
hMem = GlobalAlloc(GMEM_MOVEABLE Or GMEM_ZEROINIT, 10) 
#pMem is your pointer  
pMem = GlobalLock(hMem) 
#now you can call to my_function with the pointer: 
retval = my_function(input, pMem) 

#in VB there is auto cast so this will work: 
YourCell = get_error_code(pMem) 
# Unlock memory make the pointer useless 
x = GlobalUnlock(hMem) 
# Free the memory 
x = GlobalFree(hMem)