PHP PDO与PHP 8.1枚举类型：实现对象属性自动映射的策略

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

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

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

class User
{
    private int $id;
    private string $name;
    private UserType $userType; // 声明枚举属性

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

    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 {
            // 处理其他未声明的或需要特殊处理的属性
            // 或者抛出异常，防止意外赋值
            // throw new \InvalidArgumentException("Undefined property: $key");
        }
    }

    // 可以添加getter方法来访问属性
    public function getId(): int { return $this->id; }
    public function getName(): string { return $this->name; }
    public function getUserType(): UserType { return $this->userType; }
}

// 假设 $stmt 是一个PDOStatement对象
$stmt = Database::getInstance()->prepare("SELECT id, name, userType FROM user WHERE id = 1");
$stmt->execute();

// 设置fetch模式为FETCH_CLASS和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";
}

class User
{
    private UserType $userType;

    // 使用构造函数属性提升 (PHP 8.0+) 简化代码
    public function __construct(
        private int $id,
        private string $name,
        int $userType // 传入整数值
    ) {
        $this->userType = UserType::from($userType); // 在构造函数中转换
    }

    // Getter 方法
    public function getId(): int { return $this->id; }
    public function getName(): string { return $this->name; }
    public function getUserType(): UserType { return $this->userType; }
}

class Database
{
    private static ?PDO $instance = null; // 使用 ?PDO 允许为 null
    private ?PDOStatement $stmt = null; // 存储 PDOStatement

    // 假设这是你的单例模式连接数据库的方法
    public static function getInstance(): PDO
    {
        if (self::$instance === null) {
            // 示例连接信息，请根据实际情况修改
            $dsn = 'mysql:host=localhost;dbname=testdb;charset=utf8mb4';
            $user = 'root';
            $pass = 'password';
            $options = [
                PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
                PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC, // 默认获取关联数组
                PDO::ATTR_EMULATE_PREPARES   => false,
            ];
            self::$instance = new PDO($dsn, $user, $pass, $options);
        }
        return self::$instance;
    }

    /**
     * 自定义获取对象的方法，支持构造函数注入
     * @param string $sql SQL查询语句
     * @param array $args 绑定参数
     * @param string $class_name 要实例化的类名
     * @return object|null 实例化的对象或null
     */
    public function fetchObject(string $sql, array $args = [], string $class_name = "stdClass"): ?object
    {
        $pdo = self::getInstance(); // 获取PDO实例
        $stmt = $pdo->prepare($sql);
        $stmt->execute($args); // 执行查询

        // 获取一行作为关联数组
        $row = $stmt->fetch(PDO::FETCH_ASSOC);
        $stmt->closeCursor(); // 关闭游标

        if ($row) {
            // 使用 ...$row 将关联数组解包作为构造函数参数
            // 确保 $row 的键名与构造函数参数名一致
            return new $class_name(...$row);
        }
        return null;
    }
}

// 示例调用
$db = new Database(); // 假设Database类不是完全静态的，或者通过静态方法获取实例
$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 or an error occurred.\n";
}