份额计算订单总额的设计模式答案

【问题标题】：Design pattern for share calculating order totals份额计算订单总额的设计模式
【发布时间】：2022-01-10 21:32:50
【问题描述】：

我要解决两个问题：

在现有方法之间共享数据
减少对这些方法的耦合

我可以使用什么模式来计算总数？

/** @var array $orderData */

// Ordered products total price
$orderedProductsTotal = $this->orderedProductsTotalPrice($orderData);

$total = $orderedProductsTotal;

// Shipping cost dependent on ordered products total price
$shippingCost = $this->shippingCost($orderedProductsTotal);
$total += $shippingCost;

// Client allowed credit, depends on ordered products total price
$total -= $this->credit($orderedProductsTotal);

// Available coupon depends on order data (i.e. special products in order, etc)
$total -= $this->coupon($orderData);

// Client personal discount applying on total amount, excluding shipping cost
$total -= $this->personalDiscount($total - $shippingCost);

我在想这样的事情

$calcs = [
    'OrderProductsCalc',
    'ShippingCalc',
    'CreaditCalc',
    'CouponCalc',
    'PersonalDiscountCalc',
];

$total = 0;


foreach ($calcs as $v) {
    // How to share data between calculators?
    // Separated calculated total values of each calculator
    // Order data
    // Something else
    /** @var CalculatorInterface $calculator */
    $calculator = $this->container->get($v);
    $total = $calculator->getTotal($total);
}

这是一个依赖于购物车项目的简单类

class OrderProductsCalc implements CalcInterface
{
    private Cart $cart;

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

    public function getTotal(float $total): float
    {
        $subTotal = $this->cart->getTotal();

        return $total + $subTotal;
    }
}

ShippingCalc 也很简单，因为它在OrderProductsCalc 旁边运行。

但是CreaditCalc::getTotal() 应该接收来自OrderProductsCalc::getTotal() 的$subTotal 内部值$total。

class CreaditCalc implements CalcInterface
{
    private $customer;

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

    /**
     * @var float $total The $subTotal inner value from OrderProductsCalc::getTotal()
     */
    public function getTotal(float $total): float
    {
        $balance = $this->customer->getBalance();
        if ($balance) {
            $credit = min($balance, $total);
            
            if ($credit > 0) {
                $total -= $credit;
            }
        }
        
        return $total;
    }
}

【问题讨论】：

标签： php design-patterns architecture

【解决方案1】：

`您可以利用命令模式稍微修改设计。您可以为 'OrderProductsCalc', '运费计算', '信用计算器', '优惠券计算器', '个人折扣计算'

现在您可以通过“链接命令”来进行总体计算以进行通用设计。根据计算创建具有相应命令的链。将一个命令的输出传递给下一个命令。在抽象服务类中编写命令链接的逻辑。根据不同的计算创建子类伪代码，类似于java中的（解释意图）。

abstract class Service{

constructor(commands){
    this.commands = commands
}

Command[] commands;

public final executeChain(){
    loop(command in commands){
        command.execute();
    }
    perform();
}
abstract protected void perform();

}

class CalculateTotal extends Service{
protected void perform(){
//specific
}

}

【讨论】：