Prototype Design Pattern in C++.

In Prototype Design pattern , we partially construct an object and store it somewhere.Then we clone the prototype and then customize the instance.

Motivation behind Prototype design pattern:

? Complicated objects (e.g., cars) aren’t designed from scratch - They reiterate existing designs

? An existing (partially constructed design) is a Prototype

? We make a copy (clone) the prototype and customize it

• Requires ‘deep copy’ support
• ? We make the cloning convenient (e.g., via a Factory)

Here is a very simple code to explain the idea:

#include<iostream>
#include<memory>

struct Address
{
  std::string street;
  std::string city;
  int suite;

  friend std::ostream& operator<<(std::ostream& os , const Address& obj)
  {
    return os 
           <<"street: "<<obj.street
           <<"city : "<<obj.city
           <<"suite: "<<obj.suite<<std::endl;
  }
};

struct Contact 
{
   std::string name;
   std::unique_ptr<Address> work_address;
   
   Contact(const std::string& name, const std::unique_ptr<Address>& work_address):name{name}, 
	   work_address{std::make_unique<Address>(*work_address)}
   {
     
   }

   ~Contact()
   {
   }

   Contact(const Contact& other):name{other.name}, work_address{std::make_unique<Address>(*other.work_address)}{}

   friend std::ostream& operator<<(std::ostream& os, const Contact& obj)
   {
     return os
            <<"name: " << obj.name
            <<"work address: "<<*obj.work_address;
   }
};

struct EmployeeFactory
{
   static Contact main,aux;
   
   static std::unique_ptr<Contact> NewMainOfficeEmployee(const std::string& name,int suite)
   {
      return NewEmployeee(name, suite, main);
   }

   static std::unique_ptr<Contact> NewAuxOfficeEmployee(const std::string& name,int suite)
   {
      return NewEmployeee(name, suite, aux);
   }


private:

   static std::unique_ptr<Contact> NewEmployeee(const std::string& name , int suite, Contact& office)
   {
       auto employee = std::make_unique<Contact>(office);
       employee->name = name;
       employee->work_address->suite = suite;
       return employee;
   }
};

Contact EmployeeFactory::main{ "", std::unique_ptr<Address>(new Address{"123 Street", "Delhi", 0})};
Contact EmployeeFactory::aux{ "", std::unique_ptr<Address>(new Address{"123B Delhi", "Delhi", 0})};

int main()
{
  auto sumit = EmployeeFactory::NewMainOfficeEmployee("sumit",23);
  std::cout<<"Debug: "<<*sumit<<std::endl;
  return 0;
}