例2：

Test_Observer.cpp
/*
千万要注意对象切割问题的出现。一定要理解。
*/
#include <iostream>
#include <string>
#include <vector>
using namespace std;
class Observer
{
protected:
string name;
public:
virtual void update()
{
cout<<"Observer"<<endl;
}
};
class Man:public Observer
{
public:
Man(string name)
{
this->name=name;
}
void update()
{
cout<<name<<" Man is coming"<<endl;
}
};
class Woman:public Observer
{
public:
Woman(string name)
{
this->name=name;
}
void update()
{
cout<<name<<" Woman is leaving"<<endl;
}
};
class Subject
{
private:
vector<Observer*> obser;
public:
void add(Observer &ob)
{
obser.push_back(&ob);
}
void notify()
{
for (vector<Observer*>::iterator it=obser.begin(); it!=obser.end(); it++)
{
(*it)->update();
}
}
};
int main()
{
Subject secret;
Man m1("m1--");
Man m2("m2--");
Woman w1("w1");
Woman w2("w2");
secret.add(m1);
secret.add(m2);
secret.add(w1);
secret.add(w2);
secret.notify();
return 0;
}