成员初始化表的执行顺序与顺写顺序无关

成员初始化表的执行顺序与顺写顺序无关

首先给出结论，c++的成员初始化表的初始化，顺序与没有关系，有关系的是构造函数中，变量书写的顺序，越上面的越先初始化。

演示代码：

#include<bits/stdc++.h>  
using namespace std;  

class Student
{
  int age;
  int year;
  int birthYear;
  public:Student(int,int);   
};  

Student::Student(int x ,int y): year(x), birthYear(y),age(year - birthYear) 
{
  cout<<"age = "<<age<<endl;
  cout<<"year = "<<year<<endl;
  cout<<"birthYear = "<<birthYear<<endl;
  /*
	age = 0         // 运行结果age这里为0，因为按照构造函数的顺序，
					// age在上面，应该是age先初始化，所以age(year-birthYear)先运行，
					// 但是这个时候，year，birthYear都还没有初始化，默认为0，所以age最后为0
	year = 2014
	birthYear = 1976
	*/
}

int main()
{
    Student* p = new Student (2014,1976);
    delete p;   
    return 0;
}

正确写法：

#include<bits/stdc++.h>  
using namespace std;  

class Student
{
  int year;
  int birthYear;
  int age;
  public:Student(int,int);   

};  

Student::Student(int x ,int y): year(x), birthYear(y),age(year - birthYear) 
{
  cout<<"age = "<<age<<endl;
  cout<<"year = "<<year<<endl;
  cout<<"birthYear = "<<birthYear<<endl;
}

int main()
{
    Student* p = new Student (2014,1976);
    delete p;   
    return 0;
}