C++笔记----构造函数与析构函数（三）

1、构造函数初始化列表

推荐在构造函数初始化列表中进行初始化

构造函数的执行分为两个阶段：初始化段、 普通计算段

2、对象成员及其初始化

 #include<iostream>
 using namespace std;

 class Object
 {
 public:
     Object(int num) :num_(num)
     {
         cout << "Object..." <<num_<<"..."<< endl;
     }
     ~Object()
     {
         cout << "~Object..." << num_ << "..." << endl;
     }
 private:
     int num_;
 };
 class Container
 {
 public:
     Container(int obj1=, int obj2=):obj1_(obj1), obj2_(obj2)
     {
         cout << "Container..." << endl;
     }
     ~Container()
     {
         cout << "~Container..." << endl;
     }
 private:
     Object obj1_;
     Object obj2_;
 };
 int main(void)
 {
     Container c(,);//先构造Object，再是Container析构次序相反

     return ;
 }

3、const成员、引用成员的初始化

const成员的初始化只能在初始化列表中进行

 #include<iostream>
 using namespace std;

 //对象成员（对象所对应的类没有默认构造函数）的初始化，只能在构造函数初始化列表中进行
 class Object
 {
 public:
     Object(int num=) :num_(num), kNum_(num), redNum_(num_)
     {
         //kNum_=100;  ERROR
         //redNum_ = num;  ERROR
         cout << "Object..." << num_ << "..." << endl;
     }
     ~Object()
     {
         cout << "~Object..." << num_ << "..." << endl;
     }
 private:
     int num_;
     const int kNum_;  //const成员的初始化只能在构造函数初始化列表中进行
     int& redNum_;     //引用成员的初始化只能在构造函数初始化列表中进行
 };

 int main(void)
 {
     Object obj();

     return ;
 }

加入枚举类型

#include<iostream>
using namespace std;

class Object
{
public:
    enum E_TYPE
    {
        TYPE_A=,
        TYPE_B=
    };
public:
    Object(int num=) :num_(num), kNum_(num), redNum_(num_)
    {
        cout << "Object..." << num_ << "..." << endl;
    }
    ~Object()
    {
        cout << "~Object..." << num_ << "..." << endl;
    }
    void DisplaykNum_()
    {
        cout << "kNum_" << kNum_ << endl;
    }
private:
    int num_;
    const int kNum_;
    int& redNum_;
};

int main(void)
{
    Object obj1();
    Object obj2();
    obj1.DisplaykNum_();
    obj2.DisplaykNum_();
    cout << obj1.TYPE_A << endl;
    cout << obj2.TYPE_A << endl;
    cout << Object::TYPE_A << endl;
    return ;
}