典型重构2 (方法)

析取方法

public string PlaceOrderForWidgets(int quantity,string customerNumber)
{
    var invoice=new Invoice    
　　{
    InvoiceNumber=Guid.NewGuid().ToString(),
    TotalPrice=PricePerWidget*quantity,
    Quantity=quantity
　　};
    var customer=_customerService.GetCustomer(customerNumber);
    invoice.CustomerName=customer.CustomerName;
    invoice.CustormerAddress=customer.CustormerAddress;
    invoice.CustomerBillingInformation=customer.CustomerBillingInformation;

    double tax;
    switch(invoice.CustormerAddress.State.ToUpper())
    {
        case "OH": tax=invoice.TotalPrice*.15;
            break;
        case "MI": tax=invoice.TotalPrice*.22;
            break;
        case "NV": tax=invoice.TotalPrice*.05;
            break;
        default: tax=0.0;
            break;
    }
    var shippingPrice=invoice.TotalPrice*.1;
    invoice.TotalPrice+=shippingPrice;
    invoice.TotalPrice+=tax;
    var parmentAuthorizationCode=_paymentProcessingService.ProcessPayment(invoice.TotalPrice,customer.CustomerBillingInformation);
    invoice.Approved= !string.IsNullOrEmpty(paymentAuthorizationCode);
    _invoiceService.Post(invoice);
    return invoice.InvoiceNumber;
}

析取计算订单中税负的代码

pirvate double CalculateTaxForInvoice(Invoice invoice)
{
    double tax;
    switch(invoice.CustormerAddress.State.ToUpper())
    {
    case "OH": tax=invoice.TotalPrice*.15;
        break;
    case "MI": tax=invoice.TotalPrice*.22;
        break;
    case "NV": tax=invoice.TotalPrice*.05;
        break;
    default: tax=0.0;
        break;
    }
    return tax;    
}

 析取创建并填充Invoice对象的代码
   　　修改调用ProcessPayment方法的代码

var paymentAuthorizationCode=_paymentProcessingService.ProcessPayment(invoice.ToatalPrice,invoice.CustomerBillingInformation);

//提取发货单功能
private Invoice GetInvoice(int quantity,string customerNumber)
{
    var invoice=new Invoice
            {
                InvoiceNumber=Guid.NewGuid().ToString(),
                TotalPrice=PricePerWidget*quantity,
                Quantity=quantity
            };
    var customer=_customerService.GetCustomer(customerNumber);
    invoice.CustomerName=customer.CustomerName;
    invoice.CustormerAddress=customer.CustormerAddress;
    invoice.CustomerBillingInformation=customer.CustomerBillingInformation;
    return invoice;
}

重构结果(暂时)：

public string PlaceOrderForWidgets(int quantity,string customerNumber)
{
    var invoice= GetInvoice(quantity,customerNumber);
    var tax=CalculateTaxForInvoice(invoice);
    var shippingPrice=invoice.TotalPrice*.1;
    invoice.TotalPrice+=shippingPrice;
    invoice.TotalPrice+=tax;
    var paymentAuthorizationCode=_paymentProcessingService.ProcessPayment(invoice.ToatalPrice,invoice.CustomerBillingInformation);
    invoice.Approved= !string.IsNullOrEmpty(paymentAuthorizationCode);
    _invoiceService.Post(invoice);
    return invoice.InvoiceNumber;
}