Aggregation in C++ (HAS-A Relationship)

Aggregation in C++ is the process of one class defining another as any entity reference. It’s a different technique for reusing the class. It is a type of association that denotes the existence of a HAS-A relationship.

Example of Aggregation in C++:

Let’s look at an aggregate example where the Employee class has a reference to the Address class as a data member. It will be able to reuse the members of the Address class in this fashion.

#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;  
}

Output: