继承时，构造函数和析构函数的调用顺序
1. 先调用父类的构造函数，再初始化成员，最后调用自己的构造函数
2.先调用自己的析构函数，再析构成员，最后调用父类的析构函数
3.如果父类定义了有参数的构造函数，则自己也必须自定义带参数的构造函数
4.父类的构造函数必须是参数列表形式的
5.多继承时，class D: public Base2, Base1, Base的含义是：class D: public Base2, private Base1, private Base，而不是class D: public Base2, public Base1, public Base
6.多继承时，调用顺序取决于class D: public Base2, public Base1, public Base的顺序，也就是先调用Base2,再Base1，再Base。但是有虚继承的时候，虚继承的构造函数是最优先被调用的。
include <iostream>
using namespace std;
class Base{
public:
Base(int d) : x(d){
cout << "create Base" << endl;
}
~Base(){
cout << "free Base" << endl;
}
private:
int x;
};
class Base1{
public:
Base1(int d) : y(d){
cout << "create Base1" << endl;
}
~Base1(){
cout << "free Base1" << endl;
}
private:
int y;
};
class Base2{
public:
Base2(int d) : z(d){
cout << "create Base2" << endl;
}
~Base2(){
cout << "free Base2" << endl;
}
private:
int z;
};
class D: **public** Base2, **public** Base1, **public** Base{
public:
D(int d):Base1(d), Base(d), Base2(d), b(d), b1(d), b2(d){
//编译不过
//Base1(d); //父类的构造函数必须是参数列表形式的
cout << "create D" << endl;
}
~D(){
cout << "free D" << endl;
}
private:
Base2 b;
Base1 b1;
Base b2;
};
int main(){
D d(10);
}
执行结果：
create Base2
create Base1
create Base
create Base2
create Base1
create Base
create D
free D
free Base
free Base1
free Base2
free Base
free Base1
free Base2
