设计模式学习--不求甚解

设计模式：一套被反复使用的面向对象的结构，前辈们代码设计经验的总结，能使代码更容易复用、维护以及扩展。

常用设计模式

单例模式：

#include<iostream>
#include<pthread.h>

//pthread.h为linux库，需要在window上运行VS的请参考https://blog.youkuaiyun.com/wufuhuai/article/details/79771428?utm_source=blogxgwz7

//高版本的VS建议直接使用<mutext>库中的锁方法

using namespace std;
class TestInstance{
private:
     static TestInstance* instance;
     static pthread_mutex_t mutex;
    TestInstance(){

    ptread_mutex_init(&mutex);

};
public:
     static TestInstance* GetTestInstance();
};

   TestInstance* TestInstance:: GetTestInstance(){
    if (instance == NULL)
    {
        pthread_mutex_lock(&mutex);
        if(instance == NULL){
            instance = new TestInstance();
        }
        pthread_mutex_unlock(&mutex);
    }
    return instance;
 }
   TestInstance* TestInstance::instance = NULL;//类中的静态成员一定要初始化，编译时分配内存
   pthread_mutex_t TestInstance::mutex = {0};
2）观察者模式：

#include<iostream>
#include <vector>
#include <string>
using namespace std;
class observer{
public:
   virtual void update() = 0;
};
class subject{
private:
    vector<observer*> ObserverList;
public:
    void Attach(observer* Observer){
        ObserverList.push_back(Observer);
    }
    void Detach(observer* Observer){
        
    }
    void Notify(){
        vector<observer*>::iterator iter = ObserverList.begin();

        for (;iter != ObserverList.end();iter++)
        {
            (*iter)->update();
        }
    }

};

class Teacher : public subject{
public:
    string name;
    string state;
    Teacher(string name1 = "",string state1= ""):name(name1),state(state1){};
};
class Astudent:public observer{
    public:
        Teacher* teacher;
        Astudent(Teacher* teacher1):teacher(teacher1){};
        void update();
};
void Astudent::update(){
    cout<<teacher->name << "is "<<teacher->state<<" Astudent stop playing iphone"<<endl;
}

class Bstudent:public observer{
public:
    Teacher* teacher;
    Bstudent(Teacher* teacher1):teacher(teacher1){};

    void update(){
        cout<<teacher->name<< "is "<<teacher->state<<"Bstudent stop  eating"<<endl;
    }
};

void main(){
    Teacher Lihua("lihua");
    Bstudent b(&Lihua);
    Astudent a(&Lihua);
    observer* Bobserver = &b;
    observer* Aobserver = &a;
    Lihua.Attach(Aobserver);
    Lihua.Attach(Bobserver);
    Lihua.state = "coming";
    Lihua.Notify();
    getchar();
    return;
}

https://www.runoob.com/design-pattern/decorator-pattern.html