【设计模式】观察者模式

举例：
小王借了好多钱，分别问boss1,boss2,boss3借钱，但是小王暂时没有能力还钱，如果小王有钱的话，就会通知债主，让债主来要钱。

类的实现

class Creditor//债主类
{
 public:
 virtual void takemoney()=0; 
 virtual  ~Creditor();

};
class debtor
{
 public:
 virtual  ~debtor();
 virtual void Borrow(Creditor*cred)=0;
 virtual void notifyallcreditor()=0;//通知债主使用takemoney函数

}

class xiaowang: public debtor
{
public:

 void Borrow(Creditor*cred)override//问谁借钱了，就把他记录下来
{
  allcreaditor.push_back(cred);

}

void notifyallcreditor()override//通知债主要钱
{
   for(auto e:allcreaditor)
   {
      e->takemoney();


   }

}

vector<Creditor*>allcreaditor;

}

class boss1:public Creditor
{
    public:
void takemoney()override
{

cout<<"boss 1要钱"<<endl;

}



};
class boss2:public Creditor
{
    public:
void takemoney()override
{

cout<<"boss 2要钱"<<endl;

}



};
class boss3:public Creditor
{
    public:
void takemoney()override
{

cout<<"boss 3要钱"<<endl;

}



};

int main()
{
  xiaowang x1;
  boss1 x2;
  boss2 x3;
  boss3 x4;
  x1.Borrow(&x1);
  x1.Borrow(&x2);
  x1.Borrow(&x3);
  x1.notifyallcreditor();

}

完整代码：

#include<iostream>
#include "vector"
using namespace std;
class Creditor
{
 public:
 virtual void takemoney()=0; 
 virtual ~Creditor(){};

};
class debtor
{
 public:
 virtual  ~debtor(){};
 virtual void Borrow(Creditor*cred)=0;
 virtual void notifyallcreditor()=0;

};
class xiaowang: public debtor
{
public:

 void Borrow(Creditor*cred)override
{
  allcreaditor.push_back(cred);

}

void notifyallcreditor()override
{
   for(auto e:allcreaditor)
   {
      e->takemoney();


   }

}
private:
vector<Creditor*> allcreaditor;

};
class boss1:public Creditor
{
    public:
void takemoney()override
{

cout<<"boss 1要钱"<<endl;

}



};
class boss2:public Creditor
{
    public:
void takemoney()override
{

cout<<"boss 2要钱"<<endl;

}



};
class boss3:public Creditor
{
    public:
void takemoney()override
{

cout<<"boss 3要钱"<<endl;

}

};
int main()
{
  xiaowang x1;
  boss1 x2;
  boss2 x3;
  boss3 x4;
  x1.Borrow(&x2);
  x1.Borrow(&x3);
  x1.Borrow(&x4);
  x1.notifyallcreditor();

}