为什么要担心存储库

Question

我觉得有点愚蠢地问这个问题，因为有很多资源在讨论和解释映射器和存储库，但我似乎无法理解它。所以我创建了一些示例代码来解释我的困惑。请注意，我不知道这段代码是否真的有效，我以此为例进行了编写。

这将是实体/类（Quote.php）

class Quote {
  private $id;
  private $author;
  private $content;

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

  public function getAuthor() {
    return $this->author;
  }

  public function getContent() {
    return $this->content;
  }

  public function setId(int $id) {
    $this->id = $id;
  }

  public function getAuthor(string $author) {
    $this->author = $author;
  }

  public function setContent(string $content) {
    $this->content = $content;
  }
}

这将是映射器（QuoteMapper.php）

class QuoteMapper {
  private $PDO;

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

  public function find(int $id = null, string $search = null) {
    if (!empty($id) && !empty($search)) {
      //Search for id and search word
      $stmt = $this->PDO->prepare("SELECT `id`, `author`, `content` FROM `quotes` WHERE `id` = :id AND `content` LIKE :search LIMIT 1");
      $stmt->bindParam('search', $search, PDO::PARAM_INT);
      $stmt->bindParam('id', $id, PDO::PARAM_INT);
    else if (!empty($id)) {
      //search for id only
      $stmt = $this->PDO->prepare("SELECT `id`, `author`, `content` FROM `quotes` WHERE `id` = :id AND `content` LIKE :search LIMIT 1");
      $stmt->bindParam('id', $id, PDO::PARAM_INT);
    } else if (!empty($search)) {
      //search for search word only
      $stmt = $this->PDO->prepare("SELECT `id`, `author`, `content` FROM `quotes` WHERE `id` = :id AND `content` LIKE :search LIMIT 1");
      $stmt->bindParam('search', $search, PDO::PARAM_INT);
    }

    $stmt->execute();

    $stmt->bindColumn('id', $id);
    $stmt->bindColumn('author', $author);
    $stmt->bindColumn('content', $content);
    $stmt->fetch();

    $quote = new Image();
    $quote->setId($title);
    $quote->setAuthor($source);
    $quote->setContent($alternative);

    return $image;
  }

  public function save(Quote $quote) {
    //A save function
  }

  public function delete(Quote $quote) {
    //A delete function
  }
}

最后但并非最不重要的是，这将是存储库（QuoteRepository.php）

class ArticleRepository {
  private $articleMapper;

  public function __construct(ArticleMapper $articleMapper) {
    $this->articleMapper = $articleMapper;
  }

  public function find(int $id = null, string $search = null) {
    $article = $this->articleMapper->find($id, $search);
    return $article;
  }

  public function save(Quote $quote) {
    $this->articleMapper->save($user);
  }

  public function delete(Quote $quote) {
    $this->articleMapper->delete($user);
  }
}

据我所知，我的mapper不是'错误的'，因为mapper的目的是做一些事情，比如从持久数据存储中获取和设置数据（比如MySQL）

数据映射器是一种数据访问层，它在持久数据存储（通常是关系数据库）和内存数据表示（域层）之间执行数据的双向传输。来自Wikipedia

但我的存储库实际上并没有做任何事情。它只是将函数调用传递给映射器？所以我只能假设我的映射器包含应该在存储库中的代码，但是那将是什么代码？或许我完全误解了数据映射器和存储库如何协同工作。

如果我做了其他任何错误或被认为是不良做法的事情，我想听听。我真的想弄清楚这个！ :)

Answer 1

DataMapper是一个将应用程序与具体数据库隔离的层。它将对象转换为数据库记录，将记录转换为对象。 DataMapper使我们能够使用数据库并且不知道我们使用的RDBMS。例：

interface DataMapperInterface
{

    /**
     * Find objects by a criteria
     *
     * @param array $criteria Search params
     * @return Quote[] Found entities
     */
    public function find(array $criteria);

    /**
     * Insert an object into a database
     *
     * @param Quote $object Object that will be inserted
     */
    public function insert(Quote $object);

    /**
     * Update an object date in a database
     *
     * @param Quote $object Object that will be updated
     */
    public function update(Quote $object);

    /**
     * Remove an object from a database
     *
     * @param Quote $object Object that will be removed
     */
    public function delete(Quote $object);
}

Repository是用于封装查询构建的逻辑的层。它使我们能够处理一组对象，并且不知道如何使用Database。

class Repository
{

   /**
    * @var DataMapperInterface Mapper to transform objects
    */ 
   protected $mapper;

   /**
    * Constructor
    *
    * @param DataMapperInterface $mapper Mapper to transform objects
    */
   public function __construct(DataMapperInterface $mapper)
   {
       $this->mapper = $mapper;
   }

   /**
    * Find all objects
    *
    * @return Quote[] Found entities
    */
   public function findAll()
   {
       return $this->mapper->find([]);
   }

   /**
    * Find an object by an identifier
    *
    * @return Quote[] Found entities
    */
   public function findById(integer $id)
   {
       $criteria = ['id' => $id];
       return $this->mapper->find($criteria);
   }

   /**
    * Find objects by an author name
    *
    * @return Quote[] Found entities
    */
   public function findByAuthor($name)
   {
       $criteria = ['author' => $name];
       return $this->mapper->find($criteria);
   }

   /**
    * Save an object into the repository
    */
   public function save(Quote $object)
   {
       if (empty($object->id)) {
           $this->mapper->insert($object);
       } else {
           $this->mapper->update($object);
       }
a    }

   /**
    * Remove an object from the repository
    */
   public function remove(Quote $object)
   {
       $this->mapper->delete($object);
   }
}

这是一个非常简单的实例，在实际应用中更难实现：查询更大，存储库可以与许多其他模式配合（Query Object用于查询构建，Unit of Work用于跟踪更改，Identity Map用于避免重复加载对象等）