组合类的构造函数的调用顺序

文章来源:https://bbs.csdn.net/topics/390253882

“构造函数调用顺序：先调用内嵌对象的构造函数（按内嵌时的声明顺序，先声明者先构造）。然后调用本类的构造函数。（析构函数的调用顺序相反）”

#include<iostream>
using namespace std;
class Part //部件类
{
public:
    Part() {cout<<"Part default construction called"<<endl;}
    Part(int i) {cout<<"Part: "<<i<<" construction called"<<endl;} 
    ~Part() {cout<<"Part deconstruction called"<<endl;}
private:
    int val;
};
 
class Whole
{
public:
    Whole();
    Whole(int i,int j,int k);
    ~Whole();
private:
        //这三个变量的声明顺序改变，打印输出的结果仍然一样
    Part one;    
    Part two;
    int  date;
};
 
Whole::Whole()
{    date=0;}
Whole::Whole(int i,int j,int k)
:one(j),date(k),two(i)    //这里的初始化顺序按照one(2),date(3),two(1)进行,按照i,j,k的顺序来的.
:/*one(j),*/date(k), two(i)   //默认构造one 
{ cout<<"Whole's construction called!"<<endl; }
 
Whole::~Whole()
{
    cout<<"Whole deconstruction called!"<<endl; 
}
int main(void)
{
    Whole w(1, 2, 3);
    return 1;
}

输出结果:

Part: 2 construction called
Part: 1 construction called
Whole's construction called!

Whole deconstruction called!
Part deconstruction called
Part deconstruction called

“构造函数调用顺序：先调用内嵌对象的构造函数（按内嵌时的声明顺序，先声明者先构造,比如上面的按照i,j,k）。然后调用本类的构造函数。（析构函数的调用顺序相反）”