标签：安全 避免 aaa end 多重继承 length 相同 sof rtu
1.构造顺序：按继承顺序，先继承的先构造，同样遵循先构造父类，再构造子类的规则。
2.析构顺序，与构造顺序相反。
3.内存分布：按继承顺序，先继承的分布在前，同样遵循先构造父类，再构造子类的规则。
class Sofa {
public:
Sofa() { cout << "Sofa()" << endl; }
void Sit() { cout << "Sofa Sit" << endl; }
int length = 0xaaaaaaaa;
int color = 1;
};
class Bed {
public:
Bed() { cout << "Bed()" << endl; }
void Sleep() { cout << "Bed Sleep" << endl; }
int width = 0xbbbbbbbb;
int color = 2;
};
class SofaBed : public Sofa, public Bed {
public:
SofaBed() { cout << "SofaBed()" << endl; }
int height = 0xdddddddd;
};
int main() {
SofaBed sb;
sb.Sit();
sb.Sleep();
Sofa *pSofa = &sb;
pSofa->length = 1;
Bed *pBed = &sb;//安全，指针会定位到Bed数据开始的地址
pBed->width = 2;
//sb.color = 3;// error C2385: 对“color”的访问不明确
sb.Sofa::color = 3;//指明是哪个作用域
return 0;
}
菱形继承（钻石继承）
问题：两个父类分别从祖宗类继承了一份数据，子类从两个父类继承，则子类有两份祖宗类的数据。
虚继承：解决菱形继承的问题，继承时添加virtual关键字，使相同的祖宗类成员在内存中只有一份。
虚继承时构造顺序：先构造祖宗类，再按继承顺序构造父类，最后构造孙类。
虚继承时析构顺序：与构造顺序相反。
注意：避免使用菱形继承，结构复杂且效率低下。
class Furniture {
public:
int color = 1;
};
class Sofa : virtual public Furniture {//虚继承，继承时添加virtual关键字
public:
Sofa() { cout << "Sofa()" << endl; }
void Sit() { cout << "Sofa Sit" << endl; }
int length = 0xaaaaaaaa;
};
class Bed : virtual public Furniture {//虚继承，继承时添加virtual关键字
public:
Bed() { cout << "Bed()" << endl; }
void Sleep() { cout << "Bed Sleep" << endl; }
int width = 0xbbbbbbbb;
};
class SofaBed : public Sofa, public Bed {
public:
SofaBed() { cout << "SofaBed()" << endl; }
int height = 0xdddddddd;
};
int main() {
SofaBed sb;
sb.Sit();
sb.Sleep();
Sofa *pSofa = &sb;
pSofa->length = 1;
Bed *pBed = &sb;//安全，指针会定位到Bed数据开始的地址
pBed->width = 2;
sb.color = 3;//由于虚继承，SofaBed中只有一份color了
return 0;
}
标签：安全 避免 aaa end 多重继承 length 相同 sof rtu
原文地址：https://www.cnblogs.com/Nutshelln/p/12934968.html
