#include <memory>

void memoryManagement() {
    // 自動管理動態(tài)分配的內存
    std::unique_ptr<int> ptr(new int(42));
    
    // 無需手動delete，ptr離開作用域時自動釋放內存
}

#include <fstream>

void fileOperations() {
    // 打開文件（獲取資源）
    std::ifstream file("example.txt");
    
    // 讀取文件內容
    // ...
    
    // 無需手動關閉文件，file離開作用域時自動關閉
}

#include <mutex>
#include <thread>

std::mutex mtx;

void lockExample() {
    // 自動加鎖
    std::lock_guard<std::mutex> lock(mtx);
    
    // 臨界區(qū)代碼
    // ...
    
    // 無需手動解鎖，lock離開作用域時自動解鎖
}

#include <iostream>
#include <string>

// 模擬數據庫連接資源
class DatabaseConnection {
private:
    std::string connectionString;
    bool isConnected;
    
public:
    // 構造函數：獲取資源
    DatabaseConnection(const std::string& connStr) 
        : connectionString(connStr), isConnected(true) {
        std::cout << "連接到數據庫: " << connectionString << std::endl;
        // 實際連接數據庫的代碼
    }
    
    // 析構函數：釋放資源
    ~DatabaseConnection() {
        if (isConnected) {
            std::cout << "關閉數據庫連接: " << connectionString << std::endl;
            // 實際關閉數據庫連接的代碼
            isConnected = false;
        }
    }
    
    // 禁用拷貝語義，防止資源被多次釋放
    DatabaseConnection(const DatabaseConnection&) = delete;
    DatabaseConnection& operator=(const DatabaseConnection&) = delete;
    
    // 提供移動語義，允許資源轉移
    DatabaseConnection(DatabaseConnection&& other) noexcept
        : connectionString(std::move(other.connectionString)),
          isConnected(other.isConnected) {
        other.isConnected = false;
    }
    
    DatabaseConnection& operator=(DatabaseConnection&& other) noexcept {
        if (this != &other) {
            // 釋放當前資源
            if (isConnected) {
                std::cout << "關閉數據庫連接: " << connectionString << std::endl;
                isConnected = false;
            }
            
            // 轉移資源
            connectionString = std::move(other.connectionString);
            isConnected = other.isConnected;
            other.isConnected = false;
        }
        return *this;
    }
    
    // 提供資源操作接口
    void executeQuery(const std::string& query) {
        if (isConnected) {
            std::cout << "執(zhí)行查詢: " << query << std::endl;
            // 實際執(zhí)行查詢的代碼
        } else {
            throw std::runtime_error("數據庫連接已關閉");
        }
    }
};

void databaseExample() {
    try {
        DatabaseConnection conn("server=localhost;db=test");
        conn.executeQuery("SELECT * FROM users");
        
        // conn離開作用域時自動關閉連接
    } catch (const std::exception& e) {
        std::cerr << "錯誤: " << e.what() << std::endl;
    }
}

#include <iostream>
#include <memory>
#include <stdexcept>

void exceptionSafetyExample() {
    std::unique_ptr<int[]> data(new int[1000]);
    
    // 可能拋出異常的操作
    if (/* 某些條件 */) {
        throw std::runtime_error("出錯了!");
    }
    
    // 即使發(fā)生異常，data也會被自動釋放
}

class LazyResource {
private:
    bool initialized;
    // 資源句柄
    
public:
    LazyResource() : initialized(false) {}
    
    void useResource() {
        if (!initialized) {
            // 首次使用時獲取資源
            // ...
            initialized = true;
        }
        
        // 使用資源
        // ...
    }
    
    ~LazyResource() {
        if (initialized) {
            // 釋放資源
            // ...
        }
    }
};

class SharedResource {
private:
    int* data;
    int* refCount;
    
public:
    SharedResource() : data(new int(0)), refCount(new int(1)) {}
    
    SharedResource(const SharedResource& other)
        : data(other.data), refCount(other.refCount) {
        ++(*refCount);
    }
    
    SharedResource& operator=(const SharedResource& other) {
        if (this != &other) {
            release();
            data = other.data;
            refCount = other.refCount;
            ++(*refCount);
        }
        return *this;
    }
    
    ~SharedResource() {
        release();
    }
    
private:
    void release() {
        if (--(*refCount) == 0) {
            delete data;
            delete refCount;
        }
    }
};