Strange error c2660 “function does not take 1 arguments”

Question

My base class has this function

LRESULT CBaseClass::OnTestFunction(WPARAM id, LPARAM=0)
{
...
}

When the derived class calls this function

OnTestFunction(nId);

I get an error C2660 : "function does not take 1 arguments".

Why is that ?

Answer 1

You need to put the default value in the class definition in the header file.

class CBaseClass {
    ....
    LRESULT OnTestFunction(WPARAM id, LPARAM=0);
    ....
};

Answer 2

The default value should be in the class definition:

class CBaseClass {
    LRESULT OnTestFunction(WPARAM id, LPARAM=0);
};

so that the derived class can see that signature and the default value.

Answer 3

Shouldn't be there a name of the parameter in the signature? Like:

LRESULT CBaseClass::OnTestFunction(WPARAM id, LPARAM optional = 0)
{
   ...
}