Is there a way to call a class method from a functor inside the same class?

Question

I am a little bit new in C++ so I am not sure how to handle such a problem. I have a class with several private methods. Inside one of the methods, there is a functor from which I want to call another class method. Here is the example code:

# myprogram.h
namespace new_space
{
    // Generic functor
    template<typename _Scalar, int NX = Eigen::Dynamic, int NY = Eigen::Dynamic>
    struct Functor
    {
        typedef _Scalar Scalar;
        enum {
            InputsAtCompileTime = NX,
            ValuesAtCompileTime = NY
        };
        ...
    };

    class myNewClass
    {
    private:
        void f1();
        void f2();
    };
}

# myprogram.cpp
namespace new_space
{
    void myNewClass::f1()
    {
        ...
     }

    void myNewClass::f2()
    {
        struct my_functor : Functor<double>
        {
            my_functor(void): Functor<double>(3,3) {}
            int operator()(const Eigen::VectorXd &x, Eigen::VectorXd &fvec) const
            {
                f1();
                ...
            }
        };
        ...
    }
}

When I want to make this file I get the error:

cannot call member function ‘void new_space::myNewClass::f2()’ without object

Is there a way to fix this problem?

Answer 1

You need give your functor access to the this pointer of the object creating it. Something like this:

void myNewClass::f2()
{
    struct my_functor : Functor<double>
    {
        myNewClass *self;
        my_functor(myNewClass& self): Functor<double>(3,3), self(&self) {}
        int operator()(const Eigen::VectorXd &x, Eigen::VectorXd &fvec) const
        {
            self->f2();
            ...
        }
    };

    // when creating the functor, do it like this:
    // my_functor(*this)
};