#05 单例模式
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
using namespace std;
class A{
private:
A(){
a = new A;
}
public:
static A* getInstace(){
return a;
}
private:
static A* a;
};
A* A::a = NULL;
//实现单例步骤
//1. 构造函数私有化
//2. 增加静态私有的当前类的指针变量
//3. 提供静态对外接口，可以让用户获得单例对象
//单例 分为懒汉式
class Singleton_lazy{
private:
Singleton_lazy(){}
public:
static Singleton_lazy* getInstance(){
if (pSingleton == NULL){
pSingleton = new Singleton_lazy;
}
return pSingleton;
}
private:
static Singleton_lazy* pSingleton;
};
//类外初始化
Singleton_lazy* Singleton_lazy::pSingleton = NULL;
//饿汉式
class Singleton_hungry{
private:
Singleton_hungry(){}
public:
static Singleton_hungry* getInstance(){
return pSingleton;
}
#if 0
static void freeSpace(){
if (pSingleton != NULL ){
delete pSingleton;
}
}
#endif
class Garbo{
~Garbo(){
if (pSingleton != NULL){
delete pSingleton;
}
}
};
private:
static Singleton_hungry* pSingleton;
static Garbo garbo;
};
Singleton_hungry* Singleton_hungry::pSingleton = new Singleton_hungry;
void test01(){
Singleton_lazy* p1 = Singleton_lazy::getInstance();
Singleton_lazy* p2 = Singleton_lazy::getInstance();
if (p1 == p2){
cout << "两个指针指向同一块内存空间,是单例!" << endl;
}
else{
cout << "不是单例模式！" << endl;
}
Singleton_hungry* p3 = Singleton_hungry::getInstance();
Singleton_hungry* p4 = Singleton_hungry::getInstance();
if (p3 == p4){
cout << "两个指针指向同一块内存空间,是单例!" << endl;
}
else{
cout << "不是单例模式！" << endl;
}
}
//单例对象释放问题
void test02(){}
int main(void){
test01();
return 0;
}
