C++ 聚合（HAS-A关系）

在C++中，聚合是一种将一个类定义为另一个类的任何实体引用的过程。这是重用类的另一种方式。它是一种表示HAS-A关系的关联形式。

C++聚合示例

让我们看一个聚合的例子，其中Employee类作为数据成员具有Address类的引用。通过这种方式，它可以重用Address类的成员。

#include <iostream>
using namespace std;
class Address {
    public:
   string addressLine, city, state;  
     Address(string addressLine, string city, string state)  
    {  
        this->addressLine = addressLine;  
        this->city = city;  
        this->state = state;  
    }  
};
class Employee  
    {  
        private:
        Address* address;  //Employee HAS-A Address 
        public:
        int id;  
        string name;  
        Employee(int id, string name, Address* address)  
       {  
           this->id = id;  
           this->name = name;  
           this->address = address;  
       }  
     void display()  
       {  
           cout<<id <<" "<<name<< " "<<   
             address->addressLine<< " "<< address->city<< " "<<address->state<<endl;  
       }  
   }; 
int main(void) {
    Address a1= Address("C-146, Sec-15","Noida","UP");  
    Employee e1 = Employee(101,"Nakul",&a1);  
            e1.display(); 
   return 0;
}

输出：