重构类设计以传达设计意图

Question

我有以下课程设计。完整代码可在“How to achieve this functionality using Generics?”中找到。代码工作正常并解决了“Refactoring Code to avoid Type Casting”

中提到的强制转换问题

在RetailInvestmentReturnCalculator类中，GetInvestmentProfit()方法使用CalculateBaseProfit()抽象基类中的InvestmentReturnCalculator方法。这一事实在课堂设计中并不明显。

问题

1. 如何重构此类设计以传达上述事实？
2. 什么是防止此类设计错误的设计指南？

注意：Martin Fowler: Is Design Dead?说

  

软件架构是什么意思？对我而言，建筑这个术语传达了系统核心要素的概念，即难以改变的部分。必须建立其余部分的基础

类图



抽象

public abstract class InvestmentReturnCalculator
{
    #region Public

    public double ProfitElement { get; set; }
    public abstract double GetInvestmentProfit();

    #endregion

    #region Protected

    protected  double CalculateBaseProfit()
    {
        double profit = 0;
        if (ProfitElement < 5)
        {
            profit = ProfitElement * 5 / 100;
        }
        else
        {
            profit = ProfitElement * 10 / 100;
        }
        return profit;
    }

    #endregion
}

public abstract class InvestmentReturnCalculator<T> : InvestmentReturnCalculator where T : IBusiness
{
    public T BusinessType { get; set; }
}

混凝土

public class RetailInvestmentReturnCalculator : InvestmentReturnCalculator<IRetailBusiness>
{
    public RetailInvestmentReturnCalculator(IRetailBusiness retail)
    {
        BusinessType = retail;
        //Business = new BookShop(100);
    }

    public override double GetInvestmentProfit()
    {
        ProfitElement = BusinessType.GrossRevenue;
        return CalculateBaseProfit();
    }
}

Answer 1

ProfitElement字段相当难看。我会在InvestmentReturnCalculator上将它作为一个抽象属性，并在基类中实现它（而不是设置值） - 这称为template method pattern。那么您不需要GetInvestmentProfit()方法。

public abstract class InvestmentReturnCalculator
{
    #region Public

    public abstract double ProfitElement { get; }

    #endregion

    #region Protected

    public double GetInvestmentProfit()
    {
        double profit = 0;
        if (ProfitElement < 5)
        {
            profit = ProfitElement * 5 / 100;
        }
        else
        {
            profit = ProfitElement * 10 / 100;
        }
        return profit;
    }

    #endregion
}

public abstract class InvestmentReturnCalculator<T> : InvestmentReturnCalculator where T : IBusiness
{
    public T BusinessType { get; set; }
}

public class RetailInvestmentReturnCalculator : InvestmentReturnCalculator<IRetailBusiness>
{
    public RetailInvestmentReturnCalculator(IRetailBusiness retail)
    {
        BusinessType = retail;
        //Business = new BookShop(100);
    }

    public override double ProfitElement {get { return BusinessType.GrossRevenue;}}

}