Lesson_02/Task_2/Task_2.cpp - master - AirLexa/07

Lesson_02/Task_2/Task_2.cpp
70 строк2 KB
AirLexa
урок 2
24 июн 2026, 15:40
24 июн 2026, 15:4002f1193
#include <map>
#include <string>
#include <iostream>

class VeryHeavyDatabase {
public:
    std::string GetData(const std::string& key) const noexcept {
        return "Very Big Data String: " + key;
    }
};

class CacheProxyDB : VeryHeavyDatabase {
public:
    explicit CacheProxyDB(VeryHeavyDatabase* real_object) : real_db_(real_object) {}
    std::string GetData(const std::string& key) noexcept {
        if (cache_.find(key) == cache_.end()) {
            std::cout << "Get from real object\n";
            cache_[key] = real_db_->GetData(key);
        }
        else {
            std::cout << "Get from cache\n";
        }
        return cache_.at(key);
    }

private:
    std::map<std::string, std::string> cache_;
    VeryHeavyDatabase* real_db_;
};

class TestDB : VeryHeavyDatabase {
public:
    explicit TestDB(VeryHeavyDatabase* real_object) : real_db_(real_object) {}
    std::string GetData(const std::string& key) noexcept {
        return "test_data\n";
    }
private:
    VeryHeavyDatabase* real_db_;
};

class OneShotDB : VeryHeavyDatabase {
public:
    explicit OneShotDB(VeryHeavyDatabase* real_object, size_t shots = 1) : 
        real_db_(real_object), count(shots) {}
    std::string GetData(const std::string& key) noexcept {
        if (count-- > 0) return "value";
        else return "error";
    }
private:
    int count = 0;
    VeryHeavyDatabase* real_db_;
};

int main() {
    auto real_db = VeryHeavyDatabase();
    auto cached_db = CacheProxyDB(std::addressof(real_db));
    auto test_db = TestDB(std::addressof(real_db));
    std::cout << cached_db.GetData("key") << std::endl;
    std::cout << cached_db.GetData("key") << std::endl;
    std::cout << test_db.GetData("key") << std::endl;

    auto real_db2 = VeryHeavyDatabase();
    auto limit_db = OneShotDB(std::addressof(real_db2), 2);
    std::cout << limit_db.GetData("key") << std::endl;
    std::cout << limit_db.GetData("key") << std::endl;
    std::cout << limit_db.GetData("key") << std::endl;
    std::cout << limit_db.GetData("key") << std::endl;

    return 0;
}