PDO与PHP 8.1 Enum属性：数据对象映射的实现指南

enum UserType: int
{
    case Master = 1;
    case Admin = 2;
    case Manager = 3;
}

class User
{
    private int $id;
    private string $name;
    private UserType $userType; // Enum类型属性
}

// 定义枚举
enum UserType: int
{
    case Master = 1;
    case Admin = 2;
    case Manager = 3;
}

// 定义用户类
class User
{
    private int $id;
    private string $name;
    private UserType $userType; // Enum类型属性

    public function __construct()
    {
        // 在构造函数中 unset 掉 userType 属性，
        // 这样当PDO尝试赋值时，会触发 __set() 方法
        unset($this->userType);
    }

    // 魔术方法，用于拦截对未定义属性的赋值
    public function __set(string $key, mixed $value): void
    {
        if ($key === 'userType') {
            // 将整数值转换为 UserType 枚举实例
            $this->userType = UserType::from($value);
        } else {
            // 处理其他未定义属性的赋值，或者抛出异常
            // 通常这里可以根据需要进行扩展
            throw new \InvalidArgumentException("Undefined property: " . static::class . "::$" . $key);
        }
    }

    // 可选：添加getter方法以便访问属性
    public function getId(): int { return $this->id; }
    public function getName(): string { return $this->name; }
    public function getUserType(): UserType { return $this->userType; }
}

// 假设 Database::getInstance() 返回一个PDO实例
// 并且 $stmt 是一个PDOStatement对象，已经执行了查询
$pdo = Database::getInstance(); // 示例获取PDO实例

// 准备并执行查询
$stmt = $pdo->prepare("SELECT id, name, userType FROM user WHERE id = :id");
$stmt->execute([':id' => 1]);

// 设置抓取模式为 PDO::FETCH_CLASS | PDO::FETCH_PROPS_LATE
$stmt->setFetchMode(PDO::FETCH_CLASS | PDO::FETCH_PROPS_LATE, User::class);

// 获取用户对象
$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";
}

// 定义枚举 (与方案一相同)
enum UserType: int
{
    case Master = 1;
    case Admin = 2;
    case Manager = 3;
}

// 定义用户类，修改构造函数
class User
{
    // 使用构造函数属性提升，使代码更简洁
    public function __construct(
        private int $id,
        private string $name,
        // 接收原始的 int 类型 userType
        int $userType
    ) {
        // 在构造函数中进行类型转换
        $this->userType = UserType::from($userType);
    }

    // 可选：添加getter方法以便访问属性
    public function getId(): int { return $this->id; }
    public function getName(): string { return $this->name; }
    public function getUserType(): UserType { return $this->userType; }
}

// 修改数据访问层中的 fetchObject 方法
class Database
{
    private static ?PDO $instance = null; // 假设这是PDO实例

    // 假设 getInstance() 返回一个PDO实例
    public static function getInstance(): PDO
    {
        if (self::$instance === null) {
            // 实际应用中需要配置数据库连接信息
            self::$instance = new PDO('mysql:host=localhost;dbname=test', 'user', 'pass');
            self::$instance->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            self::$instance->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC); // 默认FETCH_ASSOC
        }
        return self::$instance;
    }

    public function fetchObject(string $sql, array $args = [], string $class_name = "stdClass"): ?object
    {
        $stmt = self::getInstance()->prepare($sql);
        $stmt->execute($args); // execute() 的参数如果是空数组，传递 null 也可以
        $row = $stmt->fetch(PDO::FETCH_ASSOC); // 获取关联数组

        // 如果有数据，则创建对象并解包数组作为构造函数参数
        return $row ? new $class_name(...$row) : null;
    }
}

// 示例调用
$db = new Database(); // 实例化数据库操作类
$user = $db->fetchObject(
    sql: "SELECT id, name, userType FROM user WHERE id = :id",
    args: ['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";
}