05 observer mode

One ： An example of inefficiency caused by traversal problems

#ifdef _DEBUG  // Only in Debug（ debugging ） In mode 
#ifndef DEBUG_NEW
#define DEBUG_NEW new(_NORMAL_BLOCK,__FILE__,__LINE__)  // Redefinition new Operator 
#define new DEBUG_NEW
#endif
#endif

//#include <boost/type_index.hpp>
using namespace std;
//#pragma warning(disable : 4996) 

namespace nmsp1
{
	class Fighter;  // Class forward declaration 
	list<Fighter*> g_playerList;

	// Player parent class （ Former combatants ）
	class Fighter
	{
	public:
		Fighter(int tmpID, string tmpName) :m_iPlayerID(tmpID), m_sPlayerName(tmpName)  // Constructors 
		{
			m_iFamilyID = -1;  //-1 It means that you have not joined any family 
		}
		virtual ~Fighter() {}  // Destructor 

	public:
		void SetFamilyID(int tmpID)  // When you join a family, you should set up a family ID
		{
			m_iFamilyID = tmpID;
		}

	public:
		void SayWords(string tmpContent)  // The player said something 
		{
			if (m_iFamilyID != -1)
			{
				// The player belongs to a family , The chat content information should be transmitted to other players in the family 
				for (auto iter = g_playerList.begin(); iter != g_playerList.end(); ++iter)
				{
					if (m_iFamilyID == (*iter)->m_iFamilyID)
					{
						// Other players in the same family should also receive chat messages 
						NotifyWords((*iter), tmpContent);
					}
				}
			}
		}

	private:
		void NotifyWords(Fighter* otherPlayer, string tmpContent)  // Other players have received chat messages from the current player 
		{
			// display information 
			cout << " The player ：" << otherPlayer->m_sPlayerName << " Received player ：" << m_sPlayerName << "  Chat messages sent ：" << tmpContent << endl;
		}

	private:
		int m_iPlayerID;  // The player ID, Globally unique 
		string m_sPlayerName;  // Player name 
		int m_iFamilyID;  // family ID
	};

	//" warrior " Class player , The parent class is Fighter
	class F_Warrior :public Fighter
	{
	public:
		F_Warrior(int tmpID, string tmpName) :Fighter(tmpID, tmpName) {}  // Constructors 
	};

	//" Master " Class player , The parent class is Fighter
	class F_Mage :public Fighter
	{
	public:
		F_Mage(int tmpID, string tmpName) :Fighter(tmpID, tmpName) {}  // Constructors 
	};
}

int main()
{
	// Create gamers 
	nmsp1::Fighter* pplayerobj1 = new nmsp1::F_Warrior(10, " Zhang San ");  // In the actual game, a lot of data is taken from the database 
	pplayerobj1->SetFamilyID(100);  // Suppose the player's family ID yes 100
	nmsp1::g_playerList.push_back(pplayerobj1);  // Add to the global player list 

	nmsp1::Fighter* pplayerobj2 = new nmsp1::F_Warrior(20, " Li Si ");
	pplayerobj2->SetFamilyID(100);
	nmsp1::g_playerList.push_back(pplayerobj2);

	nmsp1::Fighter* pplayerobj3 = new nmsp1::F_Mage(30, " Wang Wu ");
	pplayerobj3->SetFamilyID(100);
	nmsp1::g_playerList.push_back(pplayerobj3);

	nmsp1::Fighter* pplayerobj4 = new nmsp1::F_Mage(50, " Zhao Liu ");
	pplayerobj4->SetFamilyID(200);  // Zhao Liu and the first three belong to two different families 
	nmsp1::g_playerList.push_back(pplayerobj4);

	// When a player chats , People of the same race should receive this message 
	pplayerobj1->SayWords(" The whole clan immediately gathered in the swamp , Prepare to attack ！");

	// Release resources 
	delete pplayerobj1;
	delete pplayerobj2;
	delete pplayerobj3;
	delete pplayerobj4;

	std::cout << " Main thread execution completed \n";
}

Two ： Bring in the observer （Observer） Pattern

The code for using the observer design pattern is as follows

#ifdef _DEBUG  // Only in Debug（ debugging ） In mode 
#ifndef DEBUG_NEW
#define DEBUG_NEW new(_NORMAL_BLOCK,__FILE__,__LINE__)  // Redefinition new Operator 
#define new DEBUG_NEW
#endif
#endif

//#include <boost/type_index.hpp>
using namespace std;
//#pragma warning(disable : 4996) 

namespace nmsp1
{
	class Fighter;  // Class forward declaration 
	list<Fighter*> g_playerList;

	// Player parent class （ Former combatants ）
	class Fighter
	{
	public:
		Fighter(int tmpID, string tmpName) :m_iPlayerID(tmpID), m_sPlayerName(tmpName)  // Constructors 
		{
			m_iFamilyID = -1;  //-1 It means that you have not joined any family 
		}
		virtual ~Fighter() {}  // Destructor 

	public:
		void SetFamilyID(int tmpID)  // When you join a family, you should set up a family ID
		{
			m_iFamilyID = tmpID;
		}

	public:
		void SayWords(string tmpContent)  // The player said something 
		{
			if (m_iFamilyID != -1)
			{
				// The player belongs to a family , The chat content information should be transmitted to other players in the family 
				for (auto iter = g_playerList.begin(); iter != g_playerList.end(); ++iter)
				{
					if (m_iFamilyID == (*iter)->m_iFamilyID)
					{
						// Other players in the same family should also receive chat messages 
						NotifyWords((*iter), tmpContent);
					}
				}
			}
		}

	private:
		void NotifyWords(Fighter* otherPlayer, string tmpContent)  // Other players have received chat messages from the current player 
		{
			// display information 
			cout << " The player ：" << otherPlayer->m_sPlayerName << " Received player ：" << m_sPlayerName << "  Chat messages sent ：" << tmpContent << endl;
		}

	private:
		int m_iPlayerID;  // The player ID, Globally unique 
		string m_sPlayerName;  // Player name 
		int m_iFamilyID;  // family ID
	};

	//" warrior " Class player , The parent class is Fighter
	class F_Warrior :public Fighter
	{
	public:
		F_Warrior(int tmpID, string tmpName) :Fighter(tmpID, tmpName) {}  // Constructors 
	};

	//" Master " Class player , The parent class is Fighter
	class F_Mage :public Fighter
	{
	public:
		F_Mage(int tmpID, string tmpName) :Fighter(tmpID, tmpName) {}  // Constructors 
	};
}

namespace nmsp2
{
	class Fighter;  // Class forward declaration 
	class Notifier  // Notifier parent class 
	{
	public:
		virtual void addToList(Fighter* player) = 0;  // Add the players to be notified to the list 
		virtual void removeFromList(Fighter* player) = 0;  // Remove players from the list who do not want to be notified 
		virtual void notify(Fighter* talker, string tmpContent) = 0;  // Some details of the notice 
		virtual ~Notifier() {}
	};

	// Player parent class 
	class Fighter
	{
	public:
		Fighter(int tmpID, string tmpName) :m_iPlayerID(tmpID), m_sPlayerName(tmpName)  // Constructors 
		{
			m_iFamilyID = -1;  //-1 It means that you have not joined any family 
		}
		virtual ~Fighter() {}  // Destructor 

	public:
		void SetFamilyID(int tmpID)  // When you join a family, you should set up a family ID
		{
			m_iFamilyID = tmpID;
		}
		int GetFamilyID()  // Get the family ID
		{
			return m_iFamilyID;
		}

	public:
		void SayWords(string tmpContent, Notifier* notifier)  // The player said something 
		{
			notifier->notify(this, tmpContent);
		}
		// Notify the player to receive the chat message sent by other players , Virtual functions , Subclasses can be overridden to implement different functions 
		virtual void NotifyWords(Fighter* talker, string tmpContent)
		{
			// display information 
			cout << " The player ：" << m_sPlayerName << " Received player ：" << talker->m_sPlayerName << "  Chat messages sent ：" << tmpContent << endl;
		}

	private:
		int m_iPlayerID;  // The player ID, Globally unique 
		string m_sPlayerName;  // Player name 
		int m_iFamilyID;  // family ID
	};

	//" warrior " Class player , The parent class is Fighter
	class F_Warrior :public Fighter
	{
	public:
		F_Warrior(int tmpID, string tmpName) :Fighter(tmpID, tmpName) {}  // Constructors 
	};

	//" Master " Class player , The parent class is Fighter
	class F_Mage :public Fighter
	{
	public:
		F_Mage(int tmpID, string tmpName) :Fighter(tmpID, tmpName) {}  // Constructors 
	};

	// Chat message notifier 
	class TalkNotifier :public Notifier
	{
	public:
		// Add players to the family list 
		virtual void addToList(Fighter* player)
		{
			int tmpfamilyid = player->GetFamilyID();
			if (tmpfamilyid != -1)  // Joined a family 
			{
				auto iter = m_familyList.find(tmpfamilyid);
				if (iter != m_familyList.end())
				{
					// The family id stay map There is already 
					iter->second.push_back(player);  // Directly add the player to the family 
				}
				else
				{
					// The family id stay map Does not exist in the 
					list<Fighter*> tmpplayerlist;
					m_familyList.insert(make_pair(tmpfamilyid, tmpplayerlist));  // With this family id by key, Add entries to map in 
					m_familyList[tmpfamilyid].push_back(player);  // Add the first player to the family 
				}
			}
		}
		// Remove players from the family list 
		virtual void removeFromList(Fighter* player)
		{
			int tmpfamilyid = player->GetFamilyID();
			if (tmpfamilyid != -1)  // Joined a family 
			{
				auto iter = m_familyList.find(tmpfamilyid);
				if (iter != m_familyList.end())
				{
					m_familyList[tmpfamilyid].remove(player);
				}
			}
		}
		// A player in the family said something , Call this function to notify everyone in the family 
		virtual void notify(Fighter* talker, string tmpContent)  //talker It's the talking player 
		{
			int tmpfamilyid = talker->GetFamilyID();
			if (tmpfamilyid != -1)  // Joined a family 
			{
				auto itermap = m_familyList.find(tmpfamilyid);
				if (itermap != m_familyList.end())
				{
					// Traverse all members of the family to which the player belongs 
					for (auto iterlist = itermap->second.begin(); iterlist != itermap->second.end(); ++iterlist)
					{
						(*iterlist)->NotifyWords(talker, tmpContent);
					}
				}
			}
		}

	private:
		//map Medium key Means family id,value Represents the list of all players in the family 
		map<int, list<Fighter*>> m_familyList;
	};
}

int main()
{
	// Create gamers 
	nmsp2::Fighter* pplayerobj1 = new nmsp2::F_Warrior(10, " Zhang San ");  // In the actual game, a lot of data is taken from the database .
	pplayerobj1->SetFamilyID(100);  // Suppose the family of the player's family ID yes 100

	nmsp2::Fighter* pplayerobj2 = new nmsp2::F_Warrior(20, " Li Si ");
	pplayerobj2->SetFamilyID(100);

	nmsp2::Fighter* pplayerobj3 = new nmsp2::F_Mage(30, " Wang Wu ");
	pplayerobj3->SetFamilyID(100);

	nmsp2::Fighter* pplayerobj4 = new nmsp2::F_Mage(50, " Zhao Liu ");
	pplayerobj4->SetFamilyID(200);  // Zhao Liu and the first three belong to two different families 

	// Create notifier 
	nmsp2::Notifier* ptalknotify = new nmsp2::TalkNotifier();

	// Players are added to the family list , Only in this way can we receive family chat messages 
	ptalknotify->addToList(pplayerobj1);
	ptalknotify->addToList(pplayerobj2);
	ptalknotify->addToList(pplayerobj3);
	ptalknotify->addToList(pplayerobj4);

	// A gamer chats , People of the same race should receive this message 
	pplayerobj1->SayWords(" The whole clan immediately gathered in the swamp , Prepare to attack ！", ptalknotify);

	cout << " Wang Wu doesn't want to receive any more chat messages from other members of the family ---" << endl;
	ptalknotify->removeFromList(pplayerobj3);  // Remove Wang Wu from the family list 
	pplayerobj2->SayWords(" Please follow the instructions of the patriarch , Go to the swamp ！", ptalknotify);

	// Release resources 
	delete pplayerobj1;
	delete pplayerobj2;
	delete pplayerobj3;
	delete pplayerobj4;
	delete ptalknotify;

	std::cout << " Main thread execution completed \n";
}

<1>pplayerobj1->SayWords(“ The whole clan immediately gathered in the swamp , Prepare to attack ！”,ptalknotify);
<2>notifier->notify(this, tmpContent);
<3>int tmpfamilyid = talker->GetFamilyID();
<4>auto itermap = m_familyList.find(tmpfamilyid);
<5>for (auto iterlist = itermap->second.begin(); iterlist != itermap->second.end(); ++iterlist) // Traverse list Containers
(*iterlist)->NotifyWords(talker,tmpContent);
<6>cout << “ The player ：” << m_sPlayerName << " Received player ：" << talker->m_sPlayerName << " Chat messages sent ：" << tmpContent << endl;

Observer design pattern definition （ Realize the intention ）： Defines a one-to-many dependency between objects , When the state of an object changes , All objects that depend on it are automatically notified .

Release - subscribe (Publish-Subscribe）

Observer mode UML chart

Observer pattern without abstracting notifier UML chart

The four roles of the observer model
a)Subject（ The theme ）： Observe the target , Here it means Notifier class .
b)ConcreteSubject（ Specific themes ）： Here it means TalkNotifier class .
c)Observer（ The observer ）： Here it means Fighter class .
d)ConcreteObserver（ Concrete observer ）： Here it means F_Warrior and F_Mage Subclass .

Observer pattern role diagram

The characteristics of the observer model
a) An abstract coupling is established between the observer and the observed object .
b) The observation target sends a notification to all observers in the observer list .
c) You can add new observers or observation targets by adding code , Comply with opening and closing principle .

3、 ... and ： Apply Lenovo

a) Rescue the escort cart of family members .
b) Recommend the news to readers who like it .
c) By changing the graphics drawn by itself to truly reflect the company's sales data .
d) The turret will only be right 30 Players within meters （ Players in the list ） The attack .