菱形继承的复制赋值运算符 C++

问：

我在钻石继承层次结构中有 4 个类。在课堂上称呼父母双方的作业操作员为作业操作员是否正确？它不会调用运算符= 2次吗？有没有更好的方法？der12base

    protected:
        int a = 1;

    public:
        base& operator=(const base& ref){
            ...
        }
};

class der1 : virtual public base{
    protected:
        int b = 2;
    
    public:
        der1& operator=(const der1& ref){
            ...
        }
};

class der2 : virtual public base{
    protected:
        int c = 3;
        
    public:
        der2& operator=(const der2& ref){
            ...
        }
};

class der12 : public der1, public der2{
    int d = 4;

    public:
        der12& operator=(const der12& ref){
            der1::operator=(ref);
            der2::operator=(ref);
            d = ref.d;
            
            return *this;
        }
};```