成员初始化表的执行顺序与顺写顺序无关

喜欢ヅ旅行 2024-03-31 11:33 71阅读 0赞

## 成员初始化表的执行顺序与速写顺序无关 ##

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;
    }