派生类的构造函数与析构函数的调用顺序

//Test1.h
#include<iostream>
using namespace std;
class Base1
{
private:
    int a1;
public:
    Base1()//(int _a):a1(_a)
    {
        cout<<"It‘s base1 built. "<<endl;
    }
    ~Base1(){cout<<"Base1 was free. "<<endl;}
};
class Base2
{
private:
    int a2;
public:
    Base2()//(int _a):a2(_a)
    {
        cout<<"It‘s base2 built. "<<endl;
    }
    ~Base2(){cout<<"Base2 was free. "<<endl;}
};
class Base3
{
private:
    int a3;
public:
    Base3()//(int _a):a3(_a)
    {
        cout<<"It‘s base3 built. "<<endl;
    }
    ~Base3(){cout<<"Base3 was free. "<<endl;}
};
class Son : public Base2,public Base1,public Base3//1.调用基类的构造函数，按他们在派生类定义的先后顺序，顺序调用。
{　　　　　
private://2.调用成员对象的构造函数，按他们在类定义中声明的先后顺序，顺序调用
    Base1 a;
    Base3 b;
    Base2 c;
public:
    Son()//:Base1(_a),Base2(_a),Base3(_a),a(_a),b(_a),c(_a)
    {
        cout<<"It‘s son built. "<<endl;//3.派生类的构造函数体中的操作
    }
    ~Son(){cout<<"Son was free. "<<endl;}
};

将父类和派生类构造函数后的“//”去掉便是
在派生类构造函数中，只要基类不是使用缺省构造函数，都要显式给出基类名和参数表
所描述的意思。

//Test.cpp
#include"Test1.h"
void main()
{
    Son son;//son(10)
}