//Observer抽象类，用作接口
class Observer
{
protected:
Account *account;
public:
Observer(Account *account):account(account) {}
virtual void handle_event()=0;
virtual void set_account_balance(double balance)=0;
virtual ~Observer()
{
cout<<"in the destructor of Observer"<<endl;
}
};
//BankAccount详细类，继承了ACcount抽象类
class BankAccount:public Account
{
public:
~BankAccount()
{
cout<<"in the destructor of BankAccount"<<endl;
}
public:
void add_observer(Observer *o)
{
observer.push_back(o);
}
void remove_observer(Observer *o)
{
for(vector<Observer*>::iterator it=observer.begin(); it!=observer.end(); it++)
{
if(o==*it)
{
observer.erase(it);
return;
}
}
}
void notify_observer()
{
for(vector<Observer*>::const_iterator it=observer.begin(); it!=observer.end(); it++)
{
(*it)->handle_event();
}
}
void set_balance(double balance)
{
this->balance=balance;
notify_observer();
}
double get_balance()
{
return balance;
}
};
class ATM:public Observer
{
public:
ATM(Account *account):Observer(account)//将acount传递给基类Observer的构造函数
{
}
~ATM()
{
cout<<"in the destructor of ATM"<<endl;
}
public:
void handle_event()
{
cout<<"ATM: the balance of bank accont is changed to "<<account->get_balance()<<endl;
}
void set_account_balance(double balance)
{
account->set_balance(balance);
}
};
class InternetBankService:public Observer
{
public:
InternetBankService(Account *account):Observer(account) {}
~InternetBankService()
{
cout<<"in the destructor InternetBankService "<<endl;
}
public:
void handle_event()
{
cout<<"IBS: the balance of bank account is changed to:"<<account->get_balance()<<endl;
}
void set_account_balance(double balance)
{
account->set_balance(balance);
}
};
Observer.cpp
#include "Observer.h"
int main(int argc， char **argv)
{
Account *account=new BankAccount();
Observer *atm_observer=new ATM(account);
Observer *ibs_observer=new InternetBankService(account);
account->add_observer(atm_observer);
account->add_observer(ibs_observer);
account->set_balance(1000.12);
cout<<"Event is triggered by atm_observer"<<endl;
cout<<"============="<<endl;
atm_observer->set_account_balance(1000.23);
cout<<"Event is triggered by ibs_observer"<<endl;
cout<<"============="<<endl;
ibs_observer->set_account_balance(1000.36);
delete atm_observer;
delete ibs_observer;
return 0;
}