使用相同代码重载多个签名的赋值运算符？

Question

Say I have a class C:

class C {
    int m_i { 0 };
};

Now this class can be used for non-volatile and volatile objects:

C x;
volatile C y;

I want to be able to assign volatile to non-volatile, non-volatile to volatile and non-volatile to non-volatile. So I overload C's assignment operator:

class C {
    int m_i { 0 };
public:
    void operator=(const volatile C& source) volatile {
        m_i = source.m_i;
    }

    void operator=(const C& source) {
        m_i = source.m_i;
    }
};

Can this be done in a DRY way, without repeating the code in the operator= functions?

Answer 1

So after thinking about it for a while, this is the best solution I could come up with:

class C {
    int m_i { 0 };

    void assignFrom(const volatile C& src, const bool volatileSrc = true, const bool volatileSelf = true) volatile {
        auto& nqSrc = volatileSrc ? src : const_cast<const C&>(src);
        auto& self = volatileSelf ? *this : *const_cast<C*>(this);
        self.m_i = nqSrc.m_i;
    }

public:
    void operator=(const C& src) volatile {
        // non-volatile to volatile assignment
        assignFrom(src, false);
    }

    C& operator=(const volatile C& src) {
        // volatile to non-volatile assignment
        assignFrom(src, true, false);
        return *this;
    }

    C& operator=(const C& src) {
        // non-volatile to non-volatile assignment
        assignFrom(src, false, false);
        return *this;
    }
};

I tested it and it seems to be working fine.