Chain of Resposibility

// ★ demo 1
#include <iostream>
#include <vector>
#include <ctime>
using namespace std;
class Base {
	Base* next;                // 1. 基类中要有"next"指针
public:
	Base() { next = 0; }
	void setNext( Base* n ) { next = n; }
	void add( Base* n )
	{
		if (next)
			next->add( n );
		else
			next = n;
	}
	// 2. 把消息处理的工作代理给链中的下一个对象
	virtual void handle( int i ) { next->handle( i ); }
};
class Handler1 : public Base {
public:
	virtual void handle( int i )
	{
		if (rand() % 3)			// 3. 如果消息自己处理不了，交给基类，由基类负责
		{
			cout << "H1 passsed " << i << "  ";
			Base::handle( i );
		}
		else
			cout << "H1 handled " << i << "  ";
	}
};
class Handler2 : public Base {
public:
	virtual void handle( int i )
	{
		if (rand() % 3)
		{
			cout << "H2 passsed " << i << "  ";
			Base::handle( i );
		}
		else
			cout << "H2 handled " << i << "  ";
	}
};
class Handler3 : public Base {
public:
	virtual void handle( int i )
	{
		if (rand() % 3)
		{
			cout << "H3 passsed " << i << "  ";
			Base::handle( i );
		}
		else
			cout << "H3 handled " << i << "  ";
	}
};
void main( void )
{
	srand( time( 0 ) );
	Handler1 root;
	Handler2 two;
	Handler3 thr;
	root.add( &two );
	root.add( &thr );
	thr.setNext( &root );
	for (int i=1; i < 10; i++)
	{
		root.handle( i );
		cout << '\n';
	}
}
// ★ demo 2
#include <iostream>
#include <vector>
#include <ctime>
using namespace std;
class Component {
	int        value;
	Component* next;             // 1. 基类中要有"next"指针
public:
	Component( int v, Component* n ) { value = v;  next = n; }
	void setNext( Component* n )     { next = n; }
	virtual void traverse()          { cout << value << ' '; }
	// 2. 把消息处理的工作代理给链中的下一个对象
	virtual void volunteer()         { next->volunteer(); }
};
class Primitive : public Component {
public:
	Primitive( int val, Component* n = 0 ) : Component( val, n ) { }
	virtual void volunteer()
	{
		Component::traverse();     // 自己先处理一部分
		if (rand() * 100 % 6 != 0) // 负责不了的部分，代理给基类
			Component::volunteer();
	}
};
class Composite : public Component {
	vector<Component*> children;
public:
	Composite( int val, Component* n = 0 ) : Component( val, n ) { }
	void add( Component* c ) { children.push_back( c ); }
	virtual void traverse()        // Composite只负责traverse的处理
	{
		Component::traverse();
		for (int i=0; i < children.size(); i++)
			children[i]->traverse();
	}
	// 3. Composite不负责处理volunteer事件，总是把这部分工作代理给基类
	virtual void volunteer() { Component::volunteer(); }
};
void main( void ) {
	srand( time( 0 ) );                             // 1
	Primitive seven( 7 );                           // |
	Primitive six( 6, &seven );                     // +-- 2
	Composite three( 3, &six );                     // |   |
	three.add( &six );  three.add( &seven );        // |   +-- 4 5
	Primitive five( 5, &three );                    // |
	Primitive four( 4, &five );                     // +-- 3
	Composite two( 2, &four );                      // |   |
	two.add( &four );   two.add( &five );           // |   +-- 6 7
	Composite one( 1, &two );                       // |
	Primitive nine( 9, &one );                      // +-- 8 9
	Primitive eight( 8, &nine );
	one.add( &two );
	one.add( &three );
	one.add( &eight );
	one.add( &nine );
	
	seven.setNext( &eight );
	
	cout << "traverse: ";
	one.traverse();
	cout << '\n';
	
	for (int i=0; i < 8; i++) {
		one.volunteer();
		cout << '\n';
	}
}
// ★ demo 3
#include <iostream>
#include <ctime>
using namespace std;
class Link {
	int		id;
	Link*	next;                       // 1. "next"指针
	static int		theBid;             // 2. 中标的人
	static Link*	bidder;             // 2. 和他的标价
public:
	Link( int num )
	{
		id = num;
		next = 0;
	}
	void addLast( Link* l )
	{
		if (next)  // 2. Handle and/or pass on
			next->addLast( l );
		else
			next = l; 
	}
	void bid()
	{
		int num = rand() % 9;           // 3. 标价
		cout << id << '-' << num << "  ";
		if (num < theBid)               // 4. 如果出的标价比以前的低
		{                               // 4. 则此人暂时中标
		   theBid = num;
		   bidder = this;
		}
		if (next)                       // 5. 再看下一个人的标价的高低
			next->bid();
		else
			bidder->execute();          // 6. 最后中标的人，获得执行的权利
	}
	void execute()
	{
		cout << id << " is executing\n";
		theBid = 999;
	}
};
int   Link::theBid = 999;               // 7. 给个最大值
Link* Link::bidder = 0;
void main( void ) {
	Link chain( 1 );
	for (int i=2; i < 7; i++)
		chain.addLast( new Link( i ) );
	srand( time( 0 ) );
	for (i=0; i < 10; i++)
		chain.bid();                   // 3. Client "launches & leaves"
}