观察者模式

引述自CSDN 刘伟技术博客http://blog.csdn.net/LoveLion

#include <iostream>
  2 #include <string.h>
  3 using namespace std;

class AllyControlCenter;
//抽象观察类
class Observer
{
    public: 
        virtual char* getName(void) const = 0;
        virtual void setName(const char *str) = 0;
        virtual void help(void) = 0; //声明支援盟友方法
        virtual void beAttacked(AllyControlCenter* acc) = 0; //声明遭受攻击方法
        virtual ~Observer(void){}
};

//战队控制中心类：目标类
class AllyControlCenter
{
    protected:
        char *allyName;//战队名称
        Observer* array[10];//定义一个集合用于存储战队成员

    public: 
        AllyControlCenter(void): allyName(NULL)
        {       
            int size = sizeof(array) / sizeof(array[0]);
            int i = 0;
            while(i < size) 
                array[i++] = NULL; 
        }       

        void setAllyName(const char* str)
        {       
            if(allyName)
                delete[]allyName;
            allyName = new char[strlen(str) + 1];
            strcpy(allyName, str);
        }       

//注册方法
        void join(Observer* obs)
        {
            int size = sizeof(array) / sizeof(array[0]);
            int i = 0;
            while(i < size)
            {
                if(array[i] == NULL)
                    break;
                i++;
            }
            if(i < size)
                array[i] = obs;
        }

//注销方法
        void quit(Observer* obs)
        {
            int size = sizeof(array) / sizeof(array[0]);
            int i = 0;
            while(i < size)
            {
                if(array[i] == obs)
                    break;
                i++;
            }
            if(i < size)
            {
                cout << obs->getName() << " quit " << allyName << " ally" << endl;
                array[i] = NULL;
            }
        }

//声明抽象通知方法
        virtual void notifyObserver(const char *str) = 0;
        virtual ~AllyControlCenter(void)
        {
            if(allyName)
                delete[]allyName;
            allyName = NULL;
        }
};  

//具体战队控制中心类:具体目标类
class ConcreteAllyControlCenter: public AllyControlCenter
{
    public:
        ConcreteAllyControlCenter(const char *str)
    {
        if(allyName)
            delete[] allyName;
        allyName = new char[strlen(str) + 1];
        strcpy(allyName, str);
        cout << allyName << " composite done!" << endl;
        cout << "---------------------" << endl;
    }

//实现通知方法  
        void notifyObserver(const char *name)
        {
            cout << allyName << " emergency, friends " << name << " being attacked!" << endl;
            int size = sizeof(array) / sizeof(array[0]);
            int i = 0;
//遍历观察者集合，调用每一个盟友（自己除外）的支援方法
            while(i < size)
            {
                if(array[i] == NULL)
                {
                    i++;
                    continue;
                }

                if(strcmp(array[i]->getName(), name) == 0)
                {
                    i++;
                    continue;
                }

                array[i]->help();
                i++;
            }
        }
};
             
 //战队成员类：具体观察者类
class Player: public Observer
{
    private:
        char *name;

    public:
        Player(const char *str): name(NULL)
    {
        if(name)
            delete[]name;
        name = new char[strlen(str) + 1];
        strcpy(name, str);
    }

        void setName(const char *str)
        {
            if(name)
                delete[]name;
            name = new char[strlen(str) + 1];
            strcpy(name, str);
        }

        char* getName(void) const
        {
            return name;
        }
        
//支援盟友方法
        void help(void)
        {
            cout << "persist! " << name << " will help you" << endl;
        }

//遭受攻击方法的实现，当遭受攻击时将调用战队中心类的通知方法notifyObserver()来通知盟友
        void beAttacked(AllyControlCenter* acc)
        {
            cout << name << " being attacked" << endl;
            acc->notifyObserver(name);
        }
        ~Player(void)
        {
            if(name)
                delete[]name;
            name = NULL;
        }
};

int main(void)
{
    AllyControlCenter* acc = NULL;
    acc = new ConcreteAllyControlCenter("302");

    Observer *player1 = new Player("zhou");
    acc->join(player1);
    
    Observer *player2 = new Player("fu");
    acc->join(player2);

    Observer *player3 = new Player("wang");
    acc->join(player3);
    
    Observer *player4 = new Player("fang");
    acc->join(player4);

    player1->beAttacked(acc);

    delete player4;
    delete player3;
    delete player2;
    delete player1;
    delete acc;
    return 0;
}