Question

class Foo {
private:
    int m_i;

public:
    Foo(int i) : m_i(i) {}
};

class FooA
{
private:
    const static Foo & m_foo;
    static Foo & m_foo2;
};

Q1> how to initialize const static reference?

Q2> How to initialize non-const static reference?

Note:
You can make changes for class FooA in order to illustrate the methods.

Answer 1

In the same way you initialize non-reference static members:

//Foo.cpp

const Foo & FooA::m_foo = fooObj1; 
Foo & FooA::m_foo2 = fooObj2;

where fooObj1 and fooObj2 are global variables of type Foo.

Note fooObj1 and fooObj2 must be initialized before m_foo and m_foo2, otherwise you might face static initialization order fiasco problem.