C++ 初始化对象中的对象、引用、常量

钱能C++ P280~P283

#include <iostream.h>
#include <string.h>

class StudentID
{
public:
    StudentID(int id = 0)
    {
        value = id;
        cout << "StudentID 构造时 id " << value << endl;
    }

    ~StudentID()
    {
        cout << "StudentID 析构时 id " << value << endl;
    }

    int value;
};

class Student
{
public:
    Student(char *pName="noName", int ssID = 0)
    {
        cout << "Student 构造时 pName " << pName << endl;
        strcpy(name,pName);
        name[sizeof(name) - 1] = '\0'; 
        StudentID id(ssID);     
    }

    ~Student()
    {
        cout << "Student 析构" << endl;
    }

    char name[20];      
    StudentID id;       //  从输出可以看出，StudentID初始化了两次
                        //  首先初始化这里，再到构造方法
};


int main()
{
    Student s("Tom",1988);
    return 0;
}

StudentID 构造时 id 0
Student 构造时 pName Tom
StudentID 构造时 id 1988
StudentID 析构时 id 1988
Student 析构
StudentID 析构时 id 0