4.2 普通拷贝

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#include <iostream>

class Address
{
public:
        std::string street, city;
        int suite;
};

class Contact
{
public:
        std::string name;
        Address address;
};

int main(void)
{
        Contact worker{"", Address{"123 East Dr", "London", 0}};
        Contact john = worker;

        john.name = "John Doe";
        john.address.suite = 10;

        return 0;
}

4.3 通过拷贝构造函数进行拷贝

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#include <iostream>

class Address
{
public:
        std::string street, city;
        int suite;
        Address(const std::string& street, const std::string& city, const int suite)
          : street{street}, city{city}, suite{suite} {}
};

class Contact
{
public:
        std::string name;
        Address* address;
        Contact(const std::string name, Address* address)
          : name{name}
          , address{address} {}
        Contact(const Contact& other)
          : name{other.name}
          , address{ new Address{*other.address} } {}

        Contact& operator=(const Contact& other)
        {
                if (this == &other)
                        return *this;
                name = other.name;
                address = other.address;
                return *this;
        }
};

int main(void)
{
        Contact worker{"", new Address{"123 East Dr", "London", 0}};
        Contact john{worker};

        john.name = "John Doe";
        (*john.address).suite = 10;
        return 0;
}

4.4 “虚”构造函数

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#include <iostream>

class Address
{
public:
        std::string street, city;
        int suite;
        Address(const std::string& street, const std::string& city, const int suite)
          : street{street}, city{city}, suite{suite} {}

        virtual Address* clone()
        {
                return new Address{street, city, suite};
        }
};

class Contact
{
public:
        std::string name;
        Address* address;
        Contact(const std::string name, Address* address)
          : name{name}
          , address{address} {}
        Contact(const Contact& other)
          : name{other.name}
          , address{ new Address{*other.address} } {}


        Contact& operator=(const Contact& other)
        {
                if (this == &other)
                        return *this;
                name = other.name;
                address = other.address;
                return *this;
        }
};

class ExtendedAddress : public Address
{
public:
        std::string country, postcode;
        ExtendedAddress(const std::string &street, const std::string &city,
          const int suite, const std::string &country,
          const std::string &postcode)
          : Address(street, city, suite)
          , country{country}, postcode{postcode} {}

        ExtendedAddress* clone() override
        {
                return new ExtendedAddress(street, city, suite,
                                           country, postcode);
        }
};

int main(void)
{
        ExtendedAddress ea{"123 West Dr", "London", 123, "UK", "SW101EG"};
        Address& a = ea;
        auto cloned = a.clone();

        return 0;
}

4.5 序列化

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#include <iostream>
#include <algorithm>
#include <string>
#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>

class Address
{
public:
        std::string street;
        std::string city;
        int suite;
private:

        friend class boost::serialization::access;
        template<class Ar> void serialize(
          Ar &ar,
          const unsigned int version)
        {
                ar & street;
                ar & city;
                ar & suite;
        }
};

class Contact
{
public:
        std::string name;
        Address* address = nullptr;
private:
        friend class boost::serialization::access;
        template<class Ar> void serialize(Ar& ar,
          const unsigned int version)
        {
                ar & name;
                ar & address;
        }
};

template <typename T> T clone(T obj)
{
        //1. Serialize the object
        std::ostringstream oss;
        boost::archive::text_oarchive oa(oss);
        oa << obj;
        std::string s = oss.str();

        //2. Deserialize it
        std::istringstream iss(oss.str());
        boost::archive::text_iarchive ia(iss);
        T result;
        ia >> result;

        return result;
}

int main(void)
{
        Contact john{"xx", new Address{"..", "..", 2}};

        Contact jane = clone(john);
        jane.name = "Jane";
        return 0;
}

4.6 原型工厂

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#include <iostream>
#include <memory>

class Address;
class Contact;
class EmployeeFactory;

class Address
{
public:
        std::string street, city;
        int suite;
        Address(const std::string& street, const std::string& city, const int suite)
          : street{street}, city{city}, suite{suite} {}

        virtual Address* clone()
        {
                return new Address{street, city, suite};
        }
};

class Contact
{
public:
        friend class EmployeeFactory;
        std::string name;
        Address* address;
        Contact(const std::string name, Address* address)
          : name{name}
          , address{address} {}
        Contact(const Contact& other)
          : name{other.name}
          , address{ new Address{*other.address} } {}


        Contact& operator=(const Contact& other)
        {
                if (this == &other)
                        return *this;
                name = other.name;
                address = other.address;
                return *this;
        }
};

class EmployeeFactory
{
        static Contact mai;
        static Contact aux;

        static std::unique_ptr<Contact> NewEmployee(
          std::string name, int suite, Contact& proto)
        {
                auto result = std::make_unique<Contact>(proto);
                result->name = name;
                result->address->suite = suite;
                return result;
        }
public:
        static std::unique_ptr<Contact> NewMainOfficeEmployee(
          std::string name, int suite)
        {
                return NewEmployee(name, suite, mai);
        }

        static std::unique_ptr<Contact> MaxAuxOfficeEmployee(
          std::string name, int suite)
        {
                return NewEmployee(name, suite, aux);
        }
};

Contact EmployeeFactory::mai{"", new Address{"123 East Dr", "London", 0}};
Contact EmployeeFactory::aux{"", new Address{"123 East Dr", "London", 0}};

int main(void)
{
        auto john = EmployeeFactory::NewMainOfficeEmployee("John Doe", 123);
        return 0;
}