Question

我正在使用nhibernate构建.net应用程序，用于将数据映射到实体。我仍然是面向对象编程的新手，现在我有了这个问题：

我有客户，订单，产品等实体。我可以通过nhibernate从数据库和列表客户等数据中获取对象。但是，如果我想列出客户的订单总数怎么办？这些不是客户实体的数据，也不是订单实体的数据。如何获取和列出这样的组合数据？他们应该拥有自己的数据传输对象，还是更好的方法呢？

Answer 1

有一个额外的实体CustomerList，持有 Customer个对象。

CustomerList将有一种方法根据订单总数对列表进行排序，这将通过访问每个memeber的订单总数并进行比较来完成。

在PHP中，我会做类似的事情（这只是一个例子，在实际代码中可能还有其他事情你需要考虑）。

<?php

/**
 * Describe a single customer object
 */
class Customer {

    /** @var Order[] List of orders */
    private $orders = array();

    /**
     * Add an order to the order list.
     *
     * @param Order $order
     */
    public function addOrder(Order $order) {
        if (!in_array($order, $this->orders, true)) {
            $this->orders[] = $order;
        }
    }

    /**
     * Get an order by numeric index.
     *
     * @param int $index
     *
     * @return Order
     */
    public function getOrder($index) {
        return $this->orders[$index];
    }

    /**
     * Get total number of orders for customer.
     *
     * @return int
     */
    public function getOrdersTotal() {
        return count($this->orders);
    }
}

/**
 * Describe a single order.
 * I didn't include any information here because it's not relevant.
 */
class Order {

}

/**
 * Describe a list of customers.
 */
class CustomerList {

    /** @var Customer[] List of customers */
    private $customers;

    /**
     * Add a customer to the list
     *
     * @param Customer $customer
     */
    public function addCustomer(Customer $customer) {
        $this->customers[] = $customer;
    }

    /**
     * The sorting function.
     * Compare the orders total and return 1/0/-1 accordingly.
     *
     * @param Customer $a
     * @param Customer $b
     *
     * @return int
     */
    public function sort($a, $b) {
        if ($a->getOrdersTotal() === $b->getOrdersTotal()) {
            return 0;
        }
        return ($a->getOrdersTotal() > $b->getOrdersTotal()) ? 1 : -1;
    }

    /**
     * Call the sorting function on the customer list
     */
    public function sortCustomers() {
        usort($this->customers, array($this, "sort"));
    }

    /**
     * Return the full customer array.
     *
     * @return Customer[]
     */
    public function getCustomers() {
        return $this->customers;
    }
}

//Instantiation
$cList = new CustomerList();

$customer1 = new Customer();
$customer2 = new Customer();
$customer3 = new Customer();

$order1 = new Order();
$order2 = new Order();
$order3 = new Order();
$order4 = new Order();
$order5 = new Order();
$order6 = new Order();

$customer1->addOrder($order1);
$customer1->addOrder($order2);

$customer2->addOrder($order3);

$customer3->addOrder($order4);
$customer3->addOrder($order5);
$customer3->addOrder($order6);

$cList->addCustomer($customer1);
$cList->addCustomer($customer2);
$cList->addCustomer($customer3);

//List customers before sorting
var_dump($cList->getCustomers());

$cList->sortCustomers();

//List customers after sorting
var_dump($cList->getCustomers());

面向对象的编程，如何使用数据进行操作

1 个答案: