DDD实践：如何合理设计值对象与处理复杂数据结构

<?php

// 示例：值对象定义
final class UserId
{
    private string $id;

    public function __construct(string $id)
    {
        if (empty($id)) {
            throw new InvalidArgumentException('User ID cannot be empty.');
        }
        $this->id = $id;
    }

    public function value(): string
    {
        return $this->id;
    }

    public function equals(UserId $other): bool
    {
        return $this->id === $other->id;
    }
}

final class Email
{
    private string $email;

    public function __construct(string $email)
    {
        if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
            throw new InvalidArgumentException('Invalid email format.');
        }
        $this->email = $email;
    }

    public function value(): string
    {
        return $this->email;
    }

    public function equals(Email $other): bool
    {
        return $this->email === $other->email;
    }
}

final class Address
{
    private string $street;
    private string $city;
    private string $postalCode;

    public function __construct(string $street, string $city, string $postalCode)
    {
        if (empty($street) || empty($city) || empty($postalCode)) {
            throw new InvalidArgumentException('Address components cannot be empty.');
        }
        $this->street = $street;
        $this->city = $city;
        $this->postalCode = $postalCode;
    }

    public function getStreet(): string
    {
        return $this->street;
    }

    public function getCity(): string
    {
        return $this->city;
    }

    public function getPostalCode(): string
    {
        return $this->postalCode;
    }

    public function fullAddress(): string
    {
        return sprintf('%s, %s, %s', $this->street, $this->city, $this->postalCode);
    }

    public function equals(Address $other): bool
    {
        return $this->street === $other->street &&
               $this->city === $other->city &&
               $this->postalCode === $other->postalCode;
    }
}

// 示例：实体定义
class User
{
    private UserId $id;
    private string $firstName; // 简单字符串，无复杂行为
    private string $lastName;  // 简单字符串，无复杂行为
    private Email $email;
    private Address $address;

    public function __construct(
        UserId $id,
        string $firstName,
        string $lastName,
        Email $email,
        Address $address
    ) {
        $this->id = $id;
        $this->firstName = $firstName;
        $this->lastName = $lastName;
        $this->email = $email;
        $this->address = $address;
    }

    public function getId(): UserId
    {
        return $this->id;
    }

    public function getFirstName(): string
    {
        return $this->firstName;
    }

    public function getLastName(): string
    {
        return $this->lastName;
    }

    public function getEmail(): Email
    {
        return $this->email;
    }

    public function getAddress(): Address
    {
        return $this->address;
    }

    // 实体行为示例
    public function updateAddress(Address $newAddress): void
    {
        $this->address = $newAddress;
    }
}

<?php

// 假设 $userData 是从数据库查询到的原始数据对象
// 例如：$userData = $this->userRepository->findRawById($id);
// $userData 结构可能像这样：
// object(stdClass)#1 (9) {
//   ["id"] => "uuid-123"
//   ["first_name"] => "John"
//   ["last_name"] => "Doe"
//   ["email"] => "john.doe@example.com"
//   ["street"] => "123 Main St"
//   ["city"] => "Anytown"
//   ["postal_code"] => "12345"
//   ["created_at"] => "2023-01-01 10:00:00"
//   ["updated_at"] => "2023-01-01 10:00:00"
// }

// 实例化值对象和实体
$userId = new UserId($userData->id);
$email = new Email($userData->email);
$address = new Address(
    $userData->street,
    $userData->city,
    $userData->postal_code
);

$user = new User(
    $userId,
    $userData->first_name, // 原始字符串
    $userData->last_name,  // 原始字符串
    $email,
    $address
);

// 现在 $user 实体已经正确构建，包含其值对象
// 你可以对 $user 进行领域操作
$user->updateAddress(new Address('456 Oak Ave', 'Othercity', '67890'));

// 假设有一个 UserRepository 负责持久化
// $this->userRepository->save($user);