C++ class static member function calling error

Question

I write a project with visual studio. In the project I build a class called CSimApplianceDlg which has two members:

static UINT RecvDataFrame(LPVOID pParam) and CSerialPort m_Port

class CSimApplianceDlg : public CDialog
{
// Construction
public:
CSimApplianceDlg(CWnd* pParent = NULL); // standard constructor

// Implementation
protected:
HICON m_hIcon;

// Added for Serial Port operation
static UINT RecvDataFrame(LPVOID pParam); // Process received data
......
private:
......
unsigned char m_SendData[MAX_LEN]; // Data to be sent
int len;                           // the length of data to be sent
public:
CSerialPort m_Port;     // CSerialPort Object
......

CSerialPort has a public member function WriteToPort to send data through serial port.

public:
void      WriteToPort(char* string);
void      WriteToPort(char* string,int n);
void      WriteToPort(LPCTSTR string);
void      WriteToPort(LPCTSTR string,int n);

I called

m_Port.WriteToPort(m_SendData,len);

in UINT CSimApplianceDlg::RecvDataFrame(LPVOID pParam). However, while building the project, just at the line of the calling, I got

1>e:\mysourcecode\smarthome\simappliance\simappliance\simappliancedlg.cpp(557) : error C2228: left of '.WriteToPort' must have class/struct/union
1>e:\mysourcecode\smarthome\simappliance\simappliance\simappliancedlg.cpp(557) : error C2597: illegal reference to non-static member 'CSimApplianceDlg::m_SendData'
1>e:\mysourcecode\smarthome\simappliance\simappliance\simappliancedlg.cpp(557) : error C2597: illegal reference to non-static member 'CSimApplianceDlg::len'

How can I deal with these errors? And which WriteToPort is called, because I am not familiar with LPCTSTR.

Answer 1

The function static UINT RecvDataFrame(LPVOID pParam) is static. It means you can call it without an instantiation of the object CSimApplianceDlg. In other words you can call CSimApplianceDlg::RecvDataFrame() from anywhere which is often the case for call back function. This means that within that function, you cannot access the member variables (m_Port). As pointed earlier, we do not have enough information to help but it's likely that the pParam passed has a pointer to the object... alternatively, if it's the only window in your app, you can try AfxGetMainWnd(). LPCTSTR is simply defined as const TCHAR *, where TCHAR is a char or a wchar_t if your are in ANSI or Unicode. Good luck!