what does "error : a nonstatic member reference must be relative to a specific object" mean?

Question

int CPMSifDlg::EncodeAndSend(char *firstName, char *lastName, char *roomNumber, char *userId, char *userFirstName, char *userLastName)
{
    ...

    return 1;
}

extern "C"
{
    __declspec(dllexport) int start(char *firstName, char *lastName, char *roomNumber, char *userId, char *userFirstName, char *userLastName)
    {
        return CPMSifDlg::EncodeAndSend(firstName, lastName, roomNumber, userId, userFirstName, userLastName);
    }
}

On line return CPMSifDlg::EncodeAndSend I have an error : Error : a nonstatic member reference must be relative to a specific object.

What does it mean?

score 60 · Accepted Answer · answered Mar 22 '12 at 08:14

60

EncodeAndSend is not a static function, which means it can be called on an instance of the class CPMSifDlg. You cannot write this:

 CPMSifDlg::EncodeAndSend(/*...*/);  //wrong - EncodeAndSend is not static

It should rather be called as:

 CPMSifDlg dlg; //create instance, assuming it has default constructor!
 dlg.EncodeAndSend(/*...*/);   //correct

answered Mar 22 '12 at 08:14

Nawaz

327,095
105
629
812

but if i remove the "CPMSifDlg", i got "error : identifier EncodeAndSend is undefined" – Oscar Yuandinata Mar 22 '12 at 08:17
like this right? `CPMSifDlg dlg; return dlg.EncodeAndSend(firstName, lastName, roomNumber, userId, userFirstName, userLastName);` it says the method is inaccessible – Oscar Yuandinata Mar 22 '12 at 08:19
@OscarYuandinata: Yes. You need to create an instance of the class, in order to call the function. Or, make the function a static member function, or simply a free function. – Nawaz Mar 22 '12 at 08:20
like this right? `CPMSifDlg dlg; return dlg.EncodeAndSend(firstName, lastName, roomNumber, userId, userFirstName, userLastName);` it says the method is inaccessible – Oscar Yuandinata Mar 22 '12 at 08:23
the question is, if they are friend classes, it will still have this error, which does not make any sense. strange – Dexter Sep 06 '20 at 13:50

score 9 · Answer 2 · answered Mar 22 '12 at 08:14

CPMSifDlg::EncodeAndSend() method is declared as non-static and thus it must be called using an object of CPMSifDlg. e.g.

CPMSifDlg obj;
return obj.EncodeAndSend(firstName, lastName, roomNumber, userId, userFirstName, userLastName);

If EncodeAndSend doesn't use/relate any specifics of an object (i.e. this) but general for the class CPMSifDlg then declare it as static:

class CPMSifDlg {
...
  static int EncodeAndSend(...);
  ^^^^^^
};

score 9 · Answer 3 · answered Mar 22 '12 at 08:27

9

Only static functions are called with class name.

classname::Staicfunction();

Non static functions have to be called using objects.

classname obj;
obj.Somefunction();

This is exactly what your error means. Since your function is non static you have to use a object reference to invoke it.

answered Mar 22 '12 at 08:27

Rohit Vipin Mathews

10,853
15
49
100

I don't think this is strictly true. If calling a non-static method in a base class from inside a derived class then the syntax Base::function() is used. – Flakker Jan 24 '18 at 10:57
if your method in derived is non static. – Rohit Vipin Mathews Jan 24 '18 at 19:46

what does "error : a nonstatic member reference must be relative to a specific object" mean?

3 Answers3

Linked