Паттерн Proxy: защитный proxy контролирует доступ к основному объекту

class Person

{

    string nameString;

    static string list[];

    static int next;

  public:

    Person()

    {

        nameString = list[next++];

    }

    string name()

    {

        return nameString;

    }

};

string Person::list[] =

{

  "Tom", "Dick", "Harry", "Bubba"

};

int Person::next = 0;

class PettyCashProtected

{

    int balance;

  public:

    PettyCashProtected()

    {

        balance = 500;

    }

    bool withdraw(int amount)

    {

        if (amount > balance)

          return false;

        balance -= amount;

        return true;

    }

    int getBalance()

    {

        return balance;

    }

};

class PettyCash

{

    PettyCashProtected realThing;

  public:

    bool withdraw(Person &p, int amount)

    {

        if (p.name() == "Tom" || p.name() == "Harry"

                              || p.name() == "Bubba")

          return realThing.withdraw(amount);

        else

          return false;

    }

    int getBalance()

    {

        return realThing.getBalance();

    }

};

int main()

{

  PettyCash pc;

  Person workers[4];

  for (int i = 0, amount = 100; i < 4; i++, amount += 100)

    if (!pc.withdraw(workers[i], amount))

      cout << "No money for " << workers[i].name() << '\n';

    else

      cout << amount << " dollars for " << workers[i].name() << '\n';

  cout << "Remaining balance is " << pc.getBalance() << '\n';

}

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100 dollars for Tom

No money for Dick

300 dollars for Harry

No money for Bubba

Remaining balance is 100

class Subject

{

  public:

    virtual void execute() = 0;

};

class RealSubject: public Subject

{

    string str;

  public:

    RealSubject(string s)

    {

        str = s;

    }

     /*virtual*/void execute()

    {

        cout << str << '\n';

    }

};

class ProxySubject: public Subject

{

    string first, second, third;

    RealSubject *ptr;

  public:

    ProxySubject(string s)

    {

        int num = s.find_first_of(' ');

        first = s.substr(0, num);

        s = s.substr(num + 1);

        num = s.find_first_of(' ');

        second = s.substr(0, num);

        s = s.substr(num + 1);

        num = s.find_first_of(' ');

        third = s.substr(0, num);

        s = s.substr(num + 1);

        ptr = new RealSubject(s);

    }

    ~ProxySubject()

    {

        delete ptr;

    }

    RealSubject *operator->()

    {

        cout << first << ' ' << second << ' ';

        return ptr;

    }

     /*virtual*/void execute()

    {

        cout << first << ' ' << third << ' ';

        ptr->execute();

    }

};

int main()

{

  ProxySubject obj(string("the quick brown fox jumped over the dog"));

  obj->execute();

  obj.execute();

}

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the quick fox jumped over the dog

the brown fox jumped over the dog