存储库和数据映射器耦合

Question

我有一个控制器获取数据以传递给视图。向其中注入（通过 pimple 容器）一项服务，该服务使用多个域模型 + 业务逻辑来创建数据。

服务本身有一个 'repository' class 注入其中，它有创建数据映射器和返回域模型实例的方法。

我知道我可能没有理解存储库的概念，因为 Martin Fowler 把它放在 "build another layer of abstraction over the mapping layer" & "A Repository mediates between the domain and data mapping layers, acting like an in-memory domain object collection." 所以我可能错误地使用了这个术语。

服务：

class InputService
    {
        private $repos;

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

        public function getInitialData()
        {
            $product = $this->repo->getProduct();
            $country = $this->repo->getCountry();
            $spinalPoint = $this->repo->getPoint();

            /*business logic with model instances to produce data array*/

            return //array of data
        }
    }

存储库：

class InputRepository
    {
        private $db;

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

        public function getCountry()
        {
            $mapper = new CountryMapper($this->db);
            $country = $mapper->fetch();
            return $country; //returns country object
        }
        // lots of other methods for returning different model objects
    }

映射器：

class CountryMapper
    {
        private $db;

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

        public function fetch()
        {
            $data = //code to grab data from db;

            $obj = new Country($data);
            return $obj;
        }
    }

如您所见，映射器与存储库紧密耦合 class，但我看不出解决它的方法。

我想知道是否有一种方法可以实现此存储库，从而提供与数据映射器 classes 更松散的耦合？

在宏伟的计划中，此应用程序相当小，因此必须更新两者的代码不会造成灾难性的后果，但您永远不会知道事情何时会发展壮大！

Answer 1

您可以在构造函数中注入 class 个名称或实例：

class InputRepository
{
    private $db;
    protected $mappers = array();

    public function __construct($db, array $mappers) {
        $this->db = $db;
        $this->mappers = $mappers;
    }

    public function getMapper($key) {
        if (!isset($this->mappers[$key]) {
           throw new Exception('Invalid mapper "'. $key .'"');
        }

        if (!$this->mappers[$key] instanceof MapperInterface) {
           $this->mappers[$key] = new $this->mappers[$key]($this->db);
        }

        return $this->mappers[$key];
    }

    public function getCountry()
    {
        $mapper = $this->getMapper('country');
        $country = $mapper->fetch();
        return $country; //returns country object
    }
    // lots of other methods for returning different model objects
}

显然，您可能希望使接口检查更加可靠。

Answer 2

数据库操作应通过适配器（MySqliAdapter、PdoAdapter 等）执行。因此，数据库连接被注入适配器，而不是映射器。当然不在存储库中，因为那样存储库的抽象目的将毫无意义。
映射器接收适配器作为依赖项，也可以接收其他映射器。
映射器作为依赖项传递给存储库。
存储库名称在语义上与域层名称相关，而不是真正与服务层名称相关。例如："InputService"：好的。 "InputRepository"：错了。 "CountryRepository"：正确。
一个服务可以接收更多的存储库。或者映射器，如果你不想应用额外的存储库层。
在代码中，唯一紧密耦合的结构是 Country 对象（实体或域对象）- 为每个获取的 table 行动态创建。即使这可以通过使用域对象工厂来避免，但我个人认为没有必要。

P.S：很抱歉没有提供更多文档化的代码。

服务

class InputService {

    private $countryRepository;
    private $productRepository;

    public function __construct(CountryRepositoryInterface $countryRepository, ProductRepositoryInterface $productRepository) {
        $this->countryRepository = $countryRepository;
        $this->productRepository = $productRepository;
    }

    public function getInitialData() {
        $products = $this->productRepository->findAll();
        $country = $this->countryRepository->findByName('England');

        //...

        return // resulted data
    }

}

存储库

class CountryRepository implements CountryRepositoryInterface {

    private $countryMapper;

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

    public function findByPrefix($prefix) {
        return $this->countryMapper->find(['prefix' => $prefix]);
    }

    public function findByName($name) {
        return $this->countryMapper->find(['name' => $name]);
    }

    public function findAll() {
        return $this->countryMapper->find();
    }

    public function store(CountryInterface $country) {
        return $this->countryMapper->save($country);
    }

    public function remove(CountryInterface $country) {
        return $this->countryMapper->delete($country);
    }

}

数据映射器

class CountryMapper implements CountryMapperInterface {

    private $adapter;
    private $countryCollection;

    public function __construct(AdapterInterface $adapter, CountryCollectionInterface $countryCollection) {
        $this->adapter = $adapter;
        $this->countryCollection = $countryCollection;
    }

    public function find(array $filter = [], $one = FALSE) {
        // If $one is TRUE then add limit to sql statement, or so...
        $rows = $this->adapter->find($sql, $bindings);

        // If $one is TRUE return a domain object, else a domain objects list.
        if ($one) {
            return $this->createCountry($row[0]);
        }

        return $this->createCountryCollection($rows);
    }

    public function save(CountryInterface $country) {
        if (NULL === $country->id) {
            // Build the INSERT statement and the bindings array...
            $this->adapter->insert($sql, $bindings);

            $lastInsertId = $this->adapter->getLastInsertId();

            return $this->find(['id' => $lastInsertId], true);
        }

        // Build the UPDATE statement and the bindings array...
        $this->adapter->update($sql, $bindings);

        return $this->find(['id' => $country->id], true);
    }

    public function delete(CountryInterface $country) {
        $sql = 'DELETE FROM countries WHERE id=:id';
        $bindings = [':id' => $country->id];

        $rowCount = $this->adapter->delete($sql, $bindings);

        return $rowCount > 0;
    }

    // Create a Country (domain object) from row.
    public function createCountry(array $row = []) {
        $country = new Country();

        /*
         * Iterate through the row items.
         * Assign a property to Country object for each item's name/value.
         */

        return $country;
    }

    // Create a Country[] list from rows list.
    public function createCountryCollection(array $rows) {
        /*
         * Iterate through rows.
         * Create a Country object for each row, with column names/values as properties.
         * Push Country object object to collection.
         * Return collection's content.
         */

        return $this->countryCollection->all();
    }

}

数据库适配器

class PdoAdapter implements AdapterInterface {

    private $connection;

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

    public function find(string $sql, array $bindings = [], int $fetchMode = PDO::FETCH_ASSOC, $fetchArgument = NULL, array $fetchConstructorArguments = []) {
        $statement = $this->connection->prepare($sql);
        $statement->execute($bindings);
        return $statement->fetchAll($fetchMode, $fetchArgument, $fetchConstructorArguments);
    }

    //...
}

域对象集合

class CountryCollection implements CountryCollectionInterface {

    private $countries = [];

    public function push(CountryInterface $country) {
        $this->countries[] = $country;
        return $this;
    }

    public function all() {
        return $this->countries;
    }

    public function getIterator() {
        return new ArrayIterator($this->countries);
    }

    //...
}

域对象

class Country implements CountryInterface {
    // Business logic: properties and methods...
}

存储库和数据映射器耦合

Repository and Data Mapper Coupling

php

model-view-controller

datamapper

decoupling

repository-pattern

服务

存储库

数据映射器

数据库适配器

域对象集合

域对象