C++ class member function callback

Question

I have the following problem. I have a function from an external library (which cannot be modified) like this:

void externalFunction(int n, void udf(double*)         


        

Answer 1

Here is how I do this, when MyClass is a singleton:

void externalFunction(int n, void udf(double) );

class MyClass
{
public:
   static MyClass* m_this;
   MyClass(){ m_this = this; }
   static void mycallback(double* x){ m_this->myrealcallback(x); }
   void myrealcallback(double* x);
}

int main()
{
   MyClass myClass;
   externalFunction(0, MyClass::mycallback);
}