Static constant members in a class C++

Question

How do I declare static constant values in C++? I want to be able to get the constant Vector3::Xaxis, but I should not be able to change it.

I\'ve seen the following cod

Answer 1

You need to initialize static members outside of class declaration.

Answer 2

class Vector3
{
public:
    double X;
    double Y;
    double Z;

    static Vector3 const Xaxis;

    Vector3(double x, double y, double z)
    {
        X = x; Y = y; Z = z;
    }
};

Vector3 const Vector3::Xaxis(1, 0, 0);

Note that last line is the definition and should be put in an implementation file (e.g. [.cpp] or [.cc]).

If you need this for a header-only module then there is a template-based trick that do it for you – but better ask separately about that if you need it.

Cheers & hth.,