设计模式：chain of responsibility模式

目的：弱化发出请求的对象和处理请求对象的之间的关系

理解：每个处理请求的对象仅仅只关注自己能处理的请求，不关系其他请求

优点：

• 无需一个管理类来匹配所有的请求，更灵活
• 责任链可以动态的调整
• Andorid中事件处理框架就使用了责任链模式

继承关系图：

例子：

class Trouble
{
	int num;
public:
	Trouble(int num)
	{
		this->num = num;
	}
	
	int getNum()
	{
		return num;
	}
};

class Handler
{
	string name;
	Handler* next;
public:
	Handler(string name)
	{
		this->name = name;
		next = NULL;
	}
	
	Handler* setNext(Handler* next)
	{
		this->next = next;
		return next;
	}
	
	void handler(Trouble* t)
	{
		if(resolve(t))
		{
			cout << "Trouble num = " << t->getNum() << " is solve by " << name << endl;
		}
		else if(next != NULL)
		{
			next->handler(t);
		}
		else
		{
			cout << "Trouble num = " << t->getNum() << " can't solve" << endl;
		}
	}
	
	virtual bool resolve(Trouble* t)
	{
		return false;
	}
};

class LittleHandler: public Handler
{
public:
	LittleHandler(string name) : Handler(name) 
	{
	}
	
	virtual bool resolve(Trouble* t)
	{
		bool ret = false;
		
		if(t->getNum() < 10)
		{
			ret = true;
		}
		
		return ret;
	}
};

class BiggerHandler: public Handler
{
public:
	BiggerHandler(string name) : Handler(name) 
	{
	}
	
	virtual bool resolve(Trouble* t)
	{
		bool ret = false;
		
		if(t->getNum() > 10)
		{
			ret = true;
		}
		
		return ret;
	}
};

int main() 
{
	Handler* h = new Handler("handler");
	LittleHandler* lh = new LittleHandler("littleHandler");
	BiggerHandler* bh = new BiggerHandler("biggerHandler");
	h->setNext(lh)->setNext(bh);
	
	Trouble* t1 = new Trouble(5);
	h->handler(t1);
	
	Trouble* t2 = new Trouble(15);
	h->handler(t2);
	
	return 0;
}