observer模式

#include <iostream>#include <list>using namespace std;// observer pattern// 抽象类 纯虚函数class observer{public:virtual void update(int a, int b, int c) = 0;};class max_observer: public observer{public:virtual void update(int a, int b, int c){int t = a > b ? a : b;cout<< (t > c ? t : c)<<endl;}};class min_observer: public observer{public:virtual void update(int a, int b, int c){int t = a < b ? a : b;cout<< ((t < c) ? t : c) <<endl;}};class average_observer: public observer{public:virtual void update(int a, int b, int c){cout<< (a+b+c)/3 <<endl;}};//-------------------------------------class subject_base{public:virtual void register_object(auto_ptr<observer> pobject) = 0;virtual void remove_object(auto_ptr<observer> pobject) = 0;virtual void notify() = 0;};class my_weight: public subject_base{public:my_weight(int a=0, int b=0, int c=0):m_weight_ago(a),m_weight_now(b),m_weight_later(c){}virtual void register_object(auto_ptr<observer> pobject){m_list.push_back(pobject);}virtual void remove_object(auto_ptr<observer> pobject){}virtual void notify(){for (list< auto_ptr<observer> >::iterator it = m_list.begin();\ it != m_list.end();\ ++it){(*it)->update(m_weight_ago, m_weight_now, m_weight_later);//  it->update(,,) error// *it->update(,,) error}}private:int m_weight_ago;int m_weight_now;int m_weight_later;list< auto_ptr<observer> > m_list;};int main(int argc, char* argv[]){// auto_ptr<observer> pa = new max_observer(); errorauto_ptr<observer> pa(new max_observer());auto_ptr<observer> pb(new min_observer());auto_ptr<observer> pc(new average_observer());auto_ptr<subject_base> psubject(new my_weight(1, 32, 100) );psubject->register_object(pa);psubject->register_object(pb);psubject->register_object(pc);psubject->notify();return 0;}