C++基础之设计模式-观察者模式_[基础][2018]c++设计模式基础入门39讲-优快云博客

本文介绍了一种使用C++实现的观察者模式。该模式通过Subject类维护一个Observer对象列表，并在状态改变时通知所有观察者更新自身状态。具体实现包括Subject基类及派生类SpecificSubject，Observer基类及派生类SpecificObserver。演示了如何创建主题对象并附加多个观察者，当主题状态变化时，观察者会接收到更新。

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#include <string>
#include <iostream>
#include <list>
 
class Observer
{
public:
	Observer() {}
	virtual ~Observer() {}
	virtual void Update() {}
};

class Subject
{
public:
	Subject() {}
	virtual ~Subject() {}
	void Attach(Observer *observer) { m_observers.push_back(observer); } 
	void Remove(Observer *observer) { m_observers.remove(observer); }  
	void Notify() {
		std::list<Observer*>::iterator iter = m_observers.begin();
		for (; iter != m_observers.end(); iter++)
			(*iter)->Update();
	}

	virtual void SetXXXXXX(std::string s) { m_xxxxxx = s; }
	virtual std::string GetXXXXXX() { return m_xxxxxx; }
protected:
	std::string m_xxxxxx;

private:
	std::list<Observer* > m_observers;
};



class SpecificObserver : public Observer
{
private:
	std::string m_name;
	Subject *m_subject;
public:
	SpecificObserver(std::string name, Subject *sub) : m_name(name), m_subject(sub) {}
	~SpecificObserver() {}
	void Update() {
		std::string status = m_subject->GetXXXXXX();
		std::cout << m_name << "-------" << status << std::endl;
	}
};

class SpecificSubject : public Subject
{
private:
	std::string m_name;
public:
	SpecificSubject(std::string name) : m_name(name) {}
	~SpecificSubject() {}

	void SetXXXXXX(std::string s) { 
		m_xxxxxx = m_name + " " + s; 
	}
	std::string GetXXXXXX() { 
		return m_xxxxxx; 
	}
};


int main()
{
	Subject *blog = new SpecificSubject("topic");
	Observer *observer1 = new SpecificObserver("cat", blog);
	Observer *observer2 = new SpecificObserver("dog", blog);
	blog->Attach(observer1);
	blog->Attach(observer2);
	blog->SetXXXXXX("call");
	blog->Notify();
	delete blog;
	delete observer1;
	return 0;
}

/*
cat-------topic call
dog-------topic call
*/