《重构-改善既有代码设计》案例之C#版（1）

《重构-改善既有代码设计》是被众多程序员推荐的一本经典。但问题是其中的一些案例是js写的。作为一个c#开发人员，看起来不太习惯。所以特意抄袭了一版C#代码。

  我想重构的一个重要的好处就是方便理解，易于修改。所以我就不说这段代码的功能是啥了（大概就是剧团根据 费用清单 计算金额，积分，并输出结果字符串）。好的代码应该就是一眼就能看出是干啥的。如果一段代码理解起来非常困难，那就说明这段代码需要重构了。

  不再废话，直接COPY代码（未重构的原始代码），之后会将重构的代码慢慢放出来。重现书中重构的手法以及效果。作为自己学习的记录。

剧目类

Play.cs

    class Play
    {
        public string name;

        public string type;
    }

演出类

Performance.cs

    class Performance
    {
        public string playID;

        public int audience;
    }

费用清单类  

Invoice.cs

    class Invoice
    {
        public string Customer;

        public List<Performance> performances=new List<Performance>();
    }

剧团类

OperaTroupe.cs 在构造函数中的是演示数据

using System;
using System.Collections.Generic;
using System.Globalization;

namespace Refactoring
{
    public class OperaTroupe
    {
        private readonly Dictionary<string, Play> _plays;

        private readonly Invoice _invoice;

        public OperaTroupe()
        {
            _invoice = new Invoice {Customer = "BigCo"};
            _invoice.performances.Add(new Performance {playID = "hamlet", audience = 55});
            _invoice.performances.Add(new Performance {playID = "as-like", audience = 35});
            _invoice.performances.Add(new Performance {playID = "othello", audience = 40});
            _plays = new Dictionary<string, Play>();
            _plays.Add("hamlet", new Play {name = "hamlet", type = "tragedy"});
            _plays.Add("as-like", new Play {name = "As You Like It", type = "comedy"});
            _plays.Add("othello", new Play {name = "Othello", type = "tragedy"});
        }

        public string Statement()
        {
            int totalAmount = 0;
            int volumeCredits = 0;
            string result = $"Statement for {_invoice.Customer} \n";
            NumberFormatInfo nfi = new CultureInfo("en-US").NumberFormat;
            nfi.CurrencyDecimalDigits = 2;

            foreach (var perf in _invoice.performances)
            {
                Play play = _plays[perf.playID];
                int thisAmount;
                switch (play.type)
                {
                    case "tragedy":
                        thisAmount = 40000;
                        if (perf.audience > 30)
                        {
                            thisAmount += 1000 * (perf.audience - 30);
                        }

                        break;
                    case "comedy":
                        thisAmount = 30000;
                        if (perf.audience > 20)
                        {
                            thisAmount += 1000 + 500 * (perf.audience - 20);
                        }

                        break;
                    default:
                        throw new Exception($"unknown type:{play.type}");
                }

                //add  volume credits
                volumeCredits += Math.Max(perf.audience - 30, 0);
                //add extra credit for every ten comedy attendees
                if ("comedy" == play.type)
                {
                    volumeCredits += perf.audience / 5;
                }

                //print line for this order
                result += $"{play.name}: {string.Format(nfi, "{0:C}", thisAmount / 100)}({perf.audience}seats)\n";
                totalAmount += thisAmount;
            }

            result += $"Amount owed is {string.Format(nfi, "{0:C}", totalAmount / 100)}\n";
            result += $"You earned {volumeCredits} credits \n";
            return result;
        }
    }
}

最后就是main函数啦

using System;

namespace Refactoring
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            string result = new OperaTroupe().Statement();
            Console.Write(result);
            Console.Read();
        }
    }
}

执行结果

 话说，像我这种不求上进的百度程序猿。一开始觉得这些代码没啥问题啊。甚至还觉得命名挺规范=.= 

 想要学好重构，就必须拥有一些程序猿的直觉，能够嗅出代码的坏味道。

 首先这个Statement方法体太长了。。。如果整个项目都是这种代码，我敢保证最多看半个小时，就觉得累了。。。

 所以这里就有 代码的坏味道之： 过长函数

 初一看，这个switch分支处理代码就可以提取出来单独作为一个方法,这个技巧就是提炼函数.然后我们就给这个方法取一个方法名，取名自古就是一个讲究的活。最好能够根据名字就知道这个方法是要干什么的。如果项目里面的方法名都是methodA这样随意的话，那阅读这些代码太浪费时间和精力了。还没看两个方法就累了。。这还怎么玩。。。这就是另外一种代码的坏味道:神秘命名。说干就干

 

        public string Statement()
        {
            int totalAmount = 0;
            int volumeCredits = 0;
            string result = $"Statement for {_invoice.Customer} \n";
            NumberFormatInfo nfi = new CultureInfo("en-US").NumberFormat;
            nfi.CurrencyDecimalDigits = 2;

            foreach (var perf in _invoice.performances)
            {
                Play play = _plays[perf.playID];
                int thisAmount = AmountFor(perf, play);

                //add  volume credits
                volumeCredits += Math.Max(perf.audience - 30, 0);
                //add extra credit for every ten comedy attendees
                if ("comedy" == play.type)
                {
                    volumeCredits += perf.audience / 5;
                }

                //print line for this order
                result += $"{play.name}: {string.Format(nfi, "{0:C}", thisAmount / 100)}({perf.audience}seats)\n";
                totalAmount += thisAmount;
            }

            result += $"Amount owed is {string.Format(nfi, "{0:C}", totalAmount / 100)}\n";
            result += $"You earned {volumeCredits} credits \n";
            return result;
        }

        private int AmountFor(Performance perf, Play play)
        {
            int thisAmount;
            switch (play.type)
            {
                case "tragedy":
                    thisAmount = 40000;
                    if (perf.audience > 30)
                    {
                        thisAmount += 1000 * (perf.audience - 30);
                    }

                    break;
                case "comedy":
                    thisAmount = 30000;
                    if (perf.audience > 20)
                    {
                        thisAmount += 1000 + 500 * (perf.audience - 20);
                    }

                    break;
                default:
                    throw new Exception($"unknown type:{play.type}");
            }

            return thisAmount;
        }

 

 这还不够,对于AmountFor这个方法,还要做两处小的修改.perf这样的缩写对于理解没有任何帮助,所以要把它改回原名aPerformance（不要缩写也是代码美学之一）.在方法内部我也觉得thisAmount改为result这样更便于理解。如此一来代码就成了这样

        public string Statement()
        {
            int totalAmount = 0;
            int volumeCredits = 0;
            string result = $"Statement for {_invoice.Customer} \n";
            NumberFormatInfo nfi = new CultureInfo("en-US").NumberFormat;
            nfi.CurrencyDecimalDigits = 2;

            foreach (var perf in _invoice.performances)
            {
                Play play = _plays[perf.playID];
                int thisAmount = AmountFor(perf, play);

                //add  volume credits
                volumeCredits += Math.Max(perf.audience - 30, 0);
                //add extra credit for every ten comedy attendees
                if ("comedy" == play.type)
                {
                    volumeCredits += perf.audience / 5;
                }

                //print line for this order
                result += $"{play.name}: {string.Format(nfi, "{0:C}", thisAmount / 100)}({perf.audience}seats)\n";
                totalAmount += thisAmount;
            }

            result += $"Amount owed is {string.Format(nfi, "{0:C}", totalAmount / 100)}\n";
            result += $"You earned {volumeCredits} credits \n";
            return result;
        }

        private int AmountFor(Performance aPerformance, Play play)
        {
            int result;
            switch (play.type)
            {
                case "tragedy":
                    result = 40000;
                    if (aPerformance.audience > 30)
                    {
                        result += 1000 * (aPerformance.audience - 30);
                    }

                    break;
                case "comedy":
                    result = 30000;
                    if (aPerformance.audience > 20)
                    {
                        result += 1000 + 500 * (aPerformance.audience - 20);
                    }

                    break;
                default:
                    throw new Exception($"unknown type:{play.type}");
            }

            return result;
        }

编译，启动，OK通过。每次做一点点修改，小步快跑

本篇完成...待续....

下一篇：《重构-改善既有代码设计》案例之C#版（2）