MVC架构中服务层的角色与数据流管理

// app/Models/UserModel.php
class UserModel {
    public function findById(int $id): ?array {
        // 模拟数据库查询
        echo "UserModel: 查询用户ID {$id}。\n";
        return ['id' => $id, 'username' => 'test_user', 'email' => 'test@example.com'];
    }

    public function createUser(array $data): bool {
        // 模拟数据库插入
        echo "UserModel: 创建用户 '{$data['username']}'。\n";
        return true;
    }
}

// app/Controllers/UserController.php
class UserController {
    private UserModel $userModel;

    public function __construct(UserModel $userModel) {
        $this->userModel = $userModel;
    }

    public function showUser(int $id) {
        // 直接从模型获取数据
        $user = $this->userModel->findById($id);
        if ($user) {
            echo "显示用户： " . json_encode($user) . "\n";
            // 渲染视图...
        } else {
            echo "用户未找到。\n";
        }
    }

    public function registerUser(array $userData) {
        // 验证和清洗逻辑可能直接在控制器中
        if (empty($userData['username']) || empty($userData['password'])) {
            echo "注册失败：用户名或密码不能为空。\n";
            return;
        }
        // 密码哈希等业务逻辑
        $userData['password'] = password_hash($userData['password'], PASSWORD_DEFAULT);

        if ($this->userModel->createUser($userData)) {
            echo "用户注册成功。\n";
            // 重定向或渲染成功视图...
        } else {
            echo "用户注册失败。\n";
        }
    }
}

// 假设调用
$userModel = new UserModel();
$userController = new UserController($userModel);
$userController->registerUser(['username' => 'newuser', 'password' => 'pass123']);
$userController->showUser(1);

// app/Models/UserModel.php (与上例相同，专注于数据持久化)
class UserModel {
    public function findById(int $id): ?array {
        echo "UserModel: 查询用户ID {$id}。\n";
        return ['id' => $id, 'username' => 'test_user', 'email' => 'test@example.com'];
    }

    public function createUser(array $data): bool {
        echo "UserModel: 创建用户 '{$data['username']}'。\n";
        return true;
    }
}

// app/Services/UserService.php
class UserService {
    private UserModel $userModel;

    public function __construct(UserModel $userModel) {
        $this->userModel = $userModel;
    }

    public function registerNewUser(string $username, string $password): bool {
        // 1. 业务逻辑：验证输入
        if (empty($username) || empty($password)) {
            echo "UserService: 验证失败 - 用户名或密码不能为空。\n";
            return false;
        }
        // 2. 业务逻辑：数据清洗/转换 (例如密码哈希)
        $hashedPassword = password_hash($password, PASSWORD_DEFAULT);
        $userData = ['username' => $username, 'password' => $hashedPassword];

        // 3. 调用模型进行数据持久化
        return $this->userModel->createUser($userData);
    }

    public function getUserProfile(int $userId): ?array {
        // 业务逻辑：例如，可以检查用户权限，或从多个模型组合数据
        echo "UserService: 获取用户ID {$userId} 的个人资料。\n";
        return $this->userModel->findById($userId);
    }
}

// app/Controllers/UserController.php
class UserController {
    private UserService $userService;

    public function __construct(UserService $userService) {
        $this->userService = $userService;
    }

    public function showUser(int $id) {
        // 控制器只负责调用服务层，获取处理后的数据
        $user = $this->userService->getUserProfile($id);
        if ($user) {
            echo "显示用户： " . json_encode($user) . "\n";
            // 渲染视图...
        } else {
            echo "用户未找到。\n";
        }
    }

    public function register() {
        // 从请求中获取数据 (例如 $_POST['username'], $_POST['password'])
        $username = 'newuser_service';
        $password = 'service_pass123';

        // 控制器将原始请求数据传递给服务层处理
        if ($this->userService->registerNewUser($username, $password)) {
            echo "用户注册成功 (通过服务层)。\n";
            // 重定向或渲染成功视图...
        } else {
            echo "用户注册失败 (通过服务层)。\n";
        }
    }
}

// 假设调用
$userModel = new UserModel();
$userService = new UserService($userModel);
$userController = new UserController($userService);
$userController->register();
$userController->showUser(1);