《重构-改善既有代码设计》案例之C#版（4）

书接上文...

这把要干个大的了,大神要把计算阶段与格式化阶段完全分离....为什么呢，因为目前这个结果是文本字符串，如果将来要新增一个需求，输出html格式的结果。那就只用新增格式化html的结果就行了。计算阶段的代码直接用就行了

这种分离的手法，叫做拆分阶段

那怎么做呢？

思路是：引入了中间数据，把代码分成2个部分，一部分计算详单所需的数据生成中间数据。一部分把中间数据渲染成想要的结果 比如文本或html

 至于手法,我太笨。。直接照抄了

要开始拆分阶段，大神先对组成第二阶段的代码引用提炼方法。这部分代码就是打印详单的代码。其实也就是statement的内容。大神把他提炼出来放在和statement同一层，新建了一个StatementData类，这个类目前没有任何内容。随着重构的过程慢慢添加

StatementData.cs

    public class StatementData
    {
        public StatementData()
        {
        }
    }

目前Statement及新提炼的方法如下（勘误：总金额不用再除100了）

        public string Statement()
        {
            StatementData statementData = new StatementData();
            return RenderPlainText(statementData);
        }

        private string RenderPlainText(StatementData statementData)
        {
            string result = $"Statement for {_invoice.Customer} \n";
            foreach (var perf in _invoice.performances)
            {
                result += $"{PlayFor(perf).name}: {Usd(AmountFor(perf))}({perf.audience}seats)\n";
            }

            result += $"Amount owed is {Usd(TotalAmount() / 100)}\n";
            result += $"You earned {TotalVolumeCredits()} credits \n";
            return result;
        }

 观察一下RenderPlainText,这个方法其实用到了customer,performances,以及调用了AmountFor(perf),TotalAmount(),TotalVolumeCredits()方法.

 所以StatementData需要填充这些内容

    public class StatementData
    {
        public string Customer;
        public List<Performance> Performances =new List<Performance>();
        public int TotalAmount;
        public int TotalVolumeCredits;

        public StatementData()
        {
        }
    }

你是不是发现了AmountFor(perf)这个没解决啊。确实,每一个Performance的金额不好搞。所以我想到的方法是，给Performane类一个Amount属性，然后用一个方法给每个Performance的Amount赋值。如下

Performance.cs

    public class Performance
    {
        public string playID;

        public int audience;

        public int amount;

    }

        private void EnrichStatementData(StatementData statementData)
        {
            foreach (var perf in statementData.Performances)
            {
                perf.amount = AmountFor(perf);
            }
            statementData.TotalAmount = TotalAmount();
            statementData.TotalVolumeCredits = TotalVolumeCredits();
        }

这时候RenderPlainText是不是完全和计算无关了（其实PlayFor(perf)也可以去掉，给Performance类一个加一个Play字段，然后在EnrichStatementData方法里给他赋值）

        private string RenderPlainText(StatementData statementData)
        {
            string result = $"Statement for {statementData.Customer} \n";
            foreach (var perf in statementData.Performances)
            {
                result += $"{perf.play.name}: {Usd(perf.amount)}({perf.audience}seats)\n";
            }

            result += $"Amount owed is {Usd(statementData.TotalAmount)}\n";
            result += $"You earned {statementData.TotalVolumeCredits} credits \n";
            return result;
        }

现在的Statement如下

        public string Statement()
        {
            StatementData statementData = new StatementData();
            statementData.Customer = _invoice.Customer;
            statementData.Performances = _invoice.performances;
            EnrichStatementData(statementData);
            return RenderPlainText(statementData);
        }

对此可以继续提炼方法

        public string Statement()
        {
            StatementData statementData = CreateStatementData();
            return RenderPlainText(statementData);
        }

        private StatementData CreateStatementData()
        {
            StatementData statementData = new StatementData();
            statementData.Customer = _invoice.Customer;
            statementData.Performances = _invoice.performances;
            EnrichStatementData(statementData);
            return statementData;
        }

这时候完成新增输出html格式的需求就十分简单了

        private string RenderHtml(StatementData statementData)
        {
            string result = $"<h1>Statement for {statementData.Customer} </h1>\n";
            result += "<table>\n";
            result += "<tr><th>play</th><th>seats</th><th>cost</th></tr>\n";
            foreach (var perf in statementData.Performances)
            {
                result += $"<tr><td>{perf.Play.name}</td><td>{perf.audience}</td><td>{Usd(perf.Amount)}</td></tr>";
            }

            result += "</table>\n";
            result += $"<p>Amount owed is <em>{Usd(statementData.TotalAmount)}</em></p>\n";
            result += $"<p>You earned <em>{statementData.TotalVolumeCredits}</em> credits </p>\n";
            return result;
        }

 

效果如下

 

 

 本篇完成...待续...

上一篇：《重构-改善既有代码设计》案例之C#版（3） 下一篇：《重构-改善既有代码设计》案例之C#版（5）