c++设计模式之观察者模式

视频地址：

https://www.ixigua.com/6804249883344634380?id=6803643021414892046

文档整理地址：

参考一：http://t.csdn.cn/1ruUO

观察者模式样例类图：

 

 样例代码：

#include<iostream>
#include <algorithm>
#include <string>
#include <list>
#include <memory>
using namespace  std;

enum class  Position
{
    CPP,
    JAVA,
    PHP,
    C_Sharp,
    Python
};

class Engineer
{
public:
    Engineer(const string &name) :name_(name) {};
    virtual void update(Position position) = 0;
protected:
    string name_;

};

class CppEngineer:public Engineer
{
public:
    CppEngineer(const string &name) :Engineer(name) {};
    virtual void update(Position position)override
    {
        if (position == Position::CPP)
        {
            cout << name_ << " 投递简历!" << endl;
        }
    }
};

class PHPEngineer :public Engineer
{
public:
    PHPEngineer(const string&name) :Engineer(name) {};
    virtual void update(Position position)override
    {
        if (position == Position::PHP)
        {
            cout << name_ << " 投递简历!" << endl;
        }
    }
};

class JAVAEngineer :public Engineer
{
public:
    JAVAEngineer(const string&name) :Engineer(name) {};
    virtual void update(Position position)override
    {
        if (position == Position::JAVA)
        {
            cout << name_ << " 投递简历!" << endl;
        }
    }
};



class Alibaba
{
public:
    void  Recruit(Position position)                //招聘某种职位
    {
        Notify(position);
    }
    void AddEngineer(shared_ptr<Engineer> engineer)
    {
        engineer_list.push_back(engineer);
    }
private:
    list<shared_ptr<Engineer>> engineer_list;
    void Notify(Position position)                //通知
    {
        for (const auto &engineer : engineer_list)
        {
            engineer->update(position);
        }
    }
};

int main()
{
    Alibaba ali;
    ali.AddEngineer(make_shared<CppEngineer>("C++程序员"));
    ali.AddEngineer(make_shared<JAVAEngineer>("Java程序员"));
    ali.AddEngineer(make_shared<PHPEngineer>("PHP程序员"));

    ali.Recruit(Position::CPP);
    ali.Recruit(Position::Python);
    ali.Recruit(Position::C_Sharp);
    ali.Recruit(Position::PHP);
}

  

参考二：

http://t.csdn.cn/1B8Eo

观察者模式样例类图：

 

 样例代码：

#include <iostream>
#include <list>
using namespace std;
 
/*抽象观察者*/
class Observer
{
public:
    virtual void Update(int) = 0;
};
 
/*抽象目标*/
class Subject
{
public:
    virtual void Attach(Observer *) = 0;  //附加观察者
    virtual void Detach(Observer *) = 0; //移除观察者
    virtual void Notify() = 0; //通知观察者
};
 
/*具体观察者*/
class ConcreteObserver : public Observer
{
public:
    ConcreteObserver(Subject *pSubject) : m_pSubject(pSubject){}
 
    void Update(int value)
    {
        cout << "ConcreteObserver get the update. New State:" << value << endl;
    }
 
private:
    Subject *m_pSubject;
};
 /*具体观察者2*/
class ConcreteObserver2 : public Observer
{
public:
    ConcreteObserver2(Subject *pSubject) : m_pSubject(pSubject){}
 
    void Update(int value)
    {
        cout << "ConcreteObserver2 get the update. New State:" << value << endl;
    }
 
private:
    Subject *m_pSubject;
};
 
/*具体目标*/
class ConcreteSubject : public Subject
{
public:
    void Attach(Observer *pObserver);
    void Detach(Observer *pObserver);
    void Notify();
 
    void SetState(int state)
    {
        m_iState = state;
    }
 
private:
    std::list<Observer *> m_ObserverList;//观察者列表
    int m_iState;
};
 
//附加观察者
void ConcreteSubject::Attach(Observer *pObserver)
{
    m_ObserverList.push_back(pObserver);
}
 
//移除观察者
void ConcreteSubject::Detach(Observer *pObserver)
{
    m_ObserverList.remove(pObserver);
}
 
//通知观察者
void ConcreteSubject::Notify()
{
    std::list<Observer *>::iterator it = m_ObserverList.begin();
    while (it != m_ObserverList.end())
    {
        (*it)->Update(m_iState);
        ++it;
    }
}
 
int main()
{
    // Create Subject  目标实例化
    ConcreteSubject *pSubject = new ConcreteSubject();
 
    // Create Observer  创建观察者
    Observer *pObserver = new ConcreteObserver(pSubject);
    Observer *pObserver2 = new ConcreteObserver2(pSubject);
 
    // Change the state 
    pSubject->SetState(2);
 
    // Register the observer
    pSubject->Attach(pObserver);
    pSubject->Attach(pObserver2);
 
    pSubject->Notify();
 
    // Unregister the observer
    pSubject->Detach(pObserver);
 
    pSubject->SetState(3);
    pSubject->Notify();
 
    delete pObserver;
    delete pObserver2;
    delete pSubject;
}

 

观察者模式：

流程：