PHP PDO与枚举类型：优雅地将数据库数据映射到带有枚举属性的对象

// 定义一个支持整数值的枚举
enum UserType: int
{
    case Master = 1;
    case Admin = 2;
    case Manager = 3;
}

// 定义一个包含UserType枚举属性的用户类
class User
{
    private int $id;
    private string $name;
    private UserType $userType; // 枚举类型属性
}

// UserType 枚举（必须是Backed Enum）
enum UserType: int
{
    case Master = 1;
    case Admin = 2;
    case Manager = 3;
}

// 改造后的 User 类
class User
{
    private int $id;
    private string $name;
    private UserType $userType;

    public function __construct()
    {
        // 在构造函数中 unset 枚举属性，以便 PDO 赋值时调用 __set
        unset($this->userType);
    }

    // __set 魔术方法用于拦截属性赋值
    public function __set($key, $value)
    {
        if ($key === 'userType') {
            // 将整数值转换为 UserType 枚举实例
            $this->userType = UserType::from($value);
        } else {
            // 处理其他未声明的属性或错误情况
            // throw new \LogicException("Property $key does not exist or cannot be set directly.");
            // 或者直接忽略，取决于业务需求
        }
    }

    // 为了演示，添加 getter 方法
    public function getId(): int { return $this->id; }
    public function getName(): string { return $this->name; }
    public function getUserType(): UserType { return $this->userType; }
}

// 示例 PDO 数据库操作
// 假设 $pdo 是一个已连接的 PDO 实例
$stmt = $pdo->prepare("SELECT id, name, userType FROM user WHERE id = :id");
$stmt->execute([':id' => 1]);

// 设置 fetch 模式为 PDO::FETCH_CLASS | PDO::FETCH_PROPS_LATE
$stmt->setFetchMode(PDO::FETCH_CLASS | PDO::FETCH_PROPS_LATE, User::class);
$user = $stmt->fetch();

if ($user instanceof User) {
    echo "User ID: " . $user->getId() . "\n";
    echo "User Name: " . $user->getName() . "\n";
    echo "User Type: " . $user->getUserType()->name . " (Value: " . $user->getUserType()->value . ")\n";
} else {
    echo "User not found.\n";
}

// UserType 枚举（必须是Backed Enum）
enum UserType: int
{
    case Master = 1;
    case Admin = 2;
    case Manager = 3;
}

// 改造后的 User 类（使用构造函数属性提升）
class User
{
    private UserType $userType;

    public function __construct(
        private int $id,
        private string $name,
        int $userType // 接收原始的整数值
    ) {
        // 在构造函数中手动将整数转换为 UserType 枚举实例
        $this->userType = UserType::from($userType);
    }

    // 为了演示，添加 getter 方法
    public function getId(): int { return $this->id; }
    public function getName(): string { return $this->name; }
    public function getUserType(): UserType { return $this->userType; }
}

// 改造后的 fetchObject 方法
class Database
{
    private static ?PDO $instance = null; // 假设已初始化并连接

    public function __construct()
    {
        // 示例：初始化 PDO 连接
        if (self::$instance === null) {
            self::$instance = new PDO('mysql:host=localhost;dbname=testdb', 'user', 'password');
            self::$instance->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            self::$instance->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC); // 默认使用关联数组
        }
    }

    public static function getInstance(): self
    {
        if (self::$instance === null) {
            new self(); // 确保 PDO 实例被初始化
        }
        return new self(); // 返回一个新的 Database 实例，或者直接返回 PDO 实例
    }

    public function fetchObject(string $sql, array $args = [], string $class_name = "stdClass"): ?object
    {
        $stmt = self::$instance->prepare($sql);
        $stmt->execute($args);

        // 使用 PDO::FETCH_ASSOC 获取关联数组
        $row = $stmt->fetch(PDO::FETCH_ASSOC);
        $stmt->closeCursor();

        // 如果获取到数据，则通过数组解包传递给目标类的构造函数
        return $row ? new $class_name(...$row) : null;
    }
}

// 示例调用
$db = new Database(); // 或者 Database::getInstance() 返回一个可操作的对象
$user = $db->fetchObject(sql: "SELECT id, name, userType FROM user WHERE id = 1", class_name: User::class);

if ($user instanceof User) {
    echo "User ID: " . $user->getId() . "\n";
    echo "User Name: " . $user->getName() . "\n";
    echo "User Type: " . $user->getUserType()->name . " (Value: " . $user->getUserType()->value . ")\n";
} else {
    echo "User not found.\n";
}