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;     } }

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<?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);