Implement interface just in place in c++

Question

I want to achieve such an outcome using c++:

Java:

public interface ITemp {
    void onCall(double value);
}

In main:

double d=2;
ITemp mVariable = new ITemp() {
@Override
    public void onCall(double value) {
    ... what to do... you can use 'd' variable...
    }
};

In C++:

class ITemp {
public:
    virtual void onCall(double something) =0;
    virtual ~ITemp();
};

In main:

double d=2;
ITemp mVariable = .... // I cannot instantiate class containing pure virtual method
// But I want to use variable d to create a method

Answer 1

You can't do exactly that since you can't create anonymous classes in C++, but you can do something similar:

int main()
{
    double d = 2;
    class T : public ITemp
    {
        double& m_v;
    public:
        T(double& v) : m_v(v) {}
        void onCall(double value)
        {
            // Do something with m_v;
            m_v *= value;
        }
    } t(d);
    t.onCall(4);
    std::cout << "d: " << d << std::endl;  // d is 8.
}

The reference ('&') makes m_v the same variable as d, but under a different name.