proxy pattern

proxy pattern

1. case 1

#include <iostream>
#include <string>

using namespace std;

class Person
{

public:
    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
{

public:
    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
{
public:
    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';
}

결과

g++ -o proxy  proxy.cpp

hacker@HACKER:~/cpp$ ./proxy
100 dollars for Tom
No money for Dick
300 dollars for Harry
No money for Bubba
Remaining balance is 100

2. case 2

#include <string>
#include <iostream>

using namespace std;

class Subject
{
public:
    virtual void execute() = 0;
};


class RealSubject: public Subject
{
public:
    string str;
	
public:
    RealSubject(string s)
    {
        str = s;
    }
	
     /*virtual*/void execute()
    {
        cout << str << '\n';
    }
};


class ProxySubject: public Subject
{
public:
    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();
}

결과

hacker@HACKER:~/cpp$ g++ -o p3 p3.cpp
hacker@HACKER:~/cpp$ ./p3
the quick fox jumped over the dog
the brown fox jumped over the dog