observer.cpp

来自「设计模式 几个常见的设计模式源代码 Delegation Factory等」· C++ 代码 · 共 69 行

#include <iostream>
using namespace std;

class Observer
{
public:
	virtual void Update() = 0;
	virtual ~Observer() {}
};

class Subject
{
public:
	virtual void Notify() = 0;
	virtual ~Subject() {}
};

class ConcreteSubject : public Subject
{
public:
	ConcreteSubject( Observer* aObserver )
	{
		_observer = aObserver;
	}
	
public:
 	void Notify()
 	{
 		_observer->Update();
 	}
	
private:
    Observer* _observer;
};

class ConsoleObserver : public Observer
{
public:
	~ConsoleObserver()
	{
		delete _subject;
	}

public:
	void Start()
	{
		_subject = new ConcreteSubject( this );
		_subject->Notify();
	}

public:
	void Update()
	{
		cout<<"the observer is called!"<<endl;
	}

private:
	Subject* _subject;
};

int main()
{
	ConsoleObserver* pObserver = new ConsoleObserver;
	pObserver->Start();	
	delete pObserver;
	
	return 0;	
}