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proxy.cpp
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proxy.cpp
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//https://refactoring.guru/design-patterns/proxy/cpp/example
//https://refactoring.guru/design-patterns/proxy
#include <algorithm>
#include <iostream>
#include <list>
#include <string>
#include <memory>
class Subject
{
public:
Subject() { std::cout << "Subject constructor\n"; }
virtual ~Subject() { std::cout << "Subject destructor\n"; }
virtual void Request() = 0;
};
class RealSubject : public Subject
{
public:
void Request() override {
std::cout << "RealSubject: Handling request\n";
}
};
class Proxy : public Subject
{
private:
std::unique_ptr<RealSubject> _real_subject;
private:
void Init() {
_real_subject.reset(new RealSubject);
}
bool CheckAcess() const {
std::cout << "Proxy: Checking access prior to firing a real request.\n";
return true;
}
void LogAccess() const {
std::cout << "Proxy: Logging the time of request.\n";
}
public:
Proxy() {}
Proxy(RealSubject* real_subject) : _real_subject{ real_subject } {}
Proxy(std::unique_ptr<RealSubject>& real_subject) : _real_subject(std::move(real_subject)) {}
~Proxy() override {}
void Request() override {
if (this->CheckAcess()) {
if (_real_subject.get() == nullptr)
Init();
_real_subject->Request();
LogAccess();
}
}
};
void ClientCode( Subject& subject) {
// ...
subject.Request();
// ...
}
int main()
{
std::unique_ptr<RealSubject> real_subject(new RealSubject);
std::cout << "Client: Executing the same client code with a proxy:\n";
std::unique_ptr<Proxy> proxy(new Proxy(real_subject));
ClientCode(*proxy);
}