调用子覆盖时始终调用超类虚函数

Question

我有这个结构：

class A
{
public:
    virtual void func(int a)
    {
        cout << "System is initiated correctly." << a;
    }
};

class B : public A
{
public:
    virtual void func(int a) override
    {
        A::func(a);
        cout << "This particular system is initiated correctly too" << a;
    }
};

现在95％的情况下，当我从A升级时，我覆盖func，在100％的情况下我应该在做其他事情之前调用A::func();？如何防止手动编写。有时我甚至忘记在子类中调用A::func();并获得运行时错误，抛出等等。

Answer 1

NVI pattern怎么样？

class A
{
public:
    void func(int a)
    {
        cout << "System is initiated correctly." << a;
        do_func(a);
    }

private:
    virtual void do_func(int a) {}
};

class B : public A
{
private:
    virtual void do_func(int a) override
    {
        cout << "This particular system is initiated correctly too" << a;
    }
};