消除Switch...Case的过程

http://www.cnblogs.com/happyframework/p/3300170.html

目录

备注需求第一遍代码（重复的代码）第二遍代码（消除重复）备注

备注返回目录

不要重复自己，也不要重复别人，一旦养成了“拷贝和粘贴”的习惯，写程序的时候非常容易导致重复，好在一直暗示自己要稍后进行重构，本文给出一个重构的示例。

需求返回目录

需求：按照年、月和日显示销售数据，根据不同的周期类型，有三个问题需要注意：

1. 默认的日期范围不同
2. 图表中显示的格式不同
3. 默认的模拟数据不同（发布环境会使用真实的数据）

如下图：

第一遍代码（重复的代码）返回目录

最爱的拷贝和粘贴。

默认的日期范围不同

 1         private void ResetStartDateAndEndDate()
 2         {
 3             this.EndDate = DateTime.Now;
 4
 5             switch (_currentCircle)
 6             {
 7                 case "日":
 8                     this.StartDate = this.EndDate.AddMonths(-1);
 9                     break;
10                 case "月":
11                     this.StartDate = this.EndDate.AddMonths(-12);
12                     break;
13                 case "年":
14                     this.StartDate = this.EndDate.AddMonths(-12 * 3);
15                     break;
16             }
17
18             this.StartDate = this.StartDate.AddDays(1);
19         }

图表中显示的格式不同

 1         public string DisplayDate
 2         {
 3             get
 4             {
 5                 switch (this.Cycle)
 6                 {
 7                     case "日":
 8                         return this.Date.ToString("yyyy-MM-dd");
 9                     case "月":
10                         return this.Date.ToString("yyyy-MM");
11                     case "年":
12                         return this.Date.ToString("yyyy");
13                     default:
14                         throw new InvalidOperationException("周期类型不匹配");
15                 }
16             }
17         }

默认的模拟数据不同

 1         public IEnumerable<SalesViewModel> Find(string cycle, DateTime startDate, DateTime endDate)
 2         {
 3             switch (cycle)
 4             {
 5                 case "日":
 6                     return new List<SalesViewModel>
 7                     {
 8                         new SalesViewModel{ Date = DateTime.Now.AddDays(-2).AddDays(1), Total = 100, Cycle = cycle },
 9                         new SalesViewModel{ Date = DateTime.Now, Total = 200, Cycle = cycle }
10                     };
11                 case "月":
12                     return new List<SalesViewModel>
13                     {
14                         new SalesViewModel{ Date = DateTime.Now.AddMonths(-2).AddDays(1), Total = 100, Cycle = cycle },
15                         new SalesViewModel{ Date = DateTime.Now, Total = 200, Cycle = cycle }
16                     };
17                 case "年":
18                     return new List<SalesViewModel>
19                     {
20                         new SalesViewModel{ Date = DateTime.Now.AddYears(-2).AddDays(1), Total = 100, Cycle = cycle },
21                         new SalesViewModel{ Date = DateTime.Now, Total = 200, Cycle = cycle }
22                     };
23                 default:
24                     return new List<SalesViewModel>();
25             }
26         }

第二遍代码（消除重复）返回目录

“门面类型+多态+私有内部类”消除重复

  1 using System;
  2 using System.Net;
  3 using System.Windows;
  4 using System.Windows.Controls;
  5 using System.Windows.Documents;
  6 using System.Windows.Ink;
  7 using System.Windows.Input;
  8 using System.Windows.Media;
  9 using System.Windows.Media.Animation;
 10 using System.Windows.Shapes;
 11 using System.Collections.Generic;
 12
 13 namespace Marking.Dashboard.Infrastructures
 14 {
 15     public static class CycleTypeHelper
 16     {
 17         private static Dictionary<string, CycleType> _CycleTypeMaps = new Dictionary<string, CycleType>
 18         {
 19             { "日", new DayCycleType() },
 20             { "月", new MonthCycleType() },
 21             { "年", new YearCycleType() }
 22         };
 23
 24         public static IEnumerable<string> CircleTypes
 25         {
 26             get
 27             {
 28                 return _CycleTypeMaps.Keys;
 29             }
 30         }
 31
 32         public static DateTime GetDefaultStartDate(string cycleType, DateTime endDate)
 33         {
 34             return _CycleTypeMaps[cycleType].GetDefaultStartDate(endDate);
 35         }
 36
 37         public static string GetDisplayDateString(string cycleType, DateTime date)
 38         {
 39             return _CycleTypeMaps[cycleType].GetDisplayDateString(date);
 40         }
 41
 42         public static IEnumerable<DateTime> SimulateDates(string cycleType, DateTime startDate, DateTime endDate)
 43         {
 44             return _CycleTypeMaps[cycleType].SimulateDates(startDate, endDate);
 45         }
 46
 47         private abstract class CycleType
 48         {
 49             public abstract DateTime GetDefaultStartDate(DateTime endDate);
 50
 51             public abstract string GetDisplayDateString(DateTime date);
 52
 53             public abstract IEnumerable<DateTime> SimulateDates(DateTime startDate, DateTime endDate);
 54         }
 55
 56         private class YearCycleType : CycleType
 57         {
 58             public override DateTime GetDefaultStartDate(DateTime endDate)
 59             {
 60                 return endDate.AddMonths(-12 * 3);
 61             }
 62
 63             public override string GetDisplayDateString(DateTime date)
 64             {
 65                 return date.ToString("yyyy");
 66             }
 67
 68             public override IEnumerable<DateTime> SimulateDates(DateTime startDate, DateTime endDate)
 69             {
 70                 for (var i = startDate; i <= endDate; i = i.AddYears(1))
 71                 {
 72                     yield return i;
 73                 }
 74             }
 75         }
 76
 77         private class MonthCycleType : CycleType
 78         {
 79             public override DateTime GetDefaultStartDate(DateTime endDate)
 80             {
 81                 return endDate.AddMonths(-12);
 82             }
 83
 84             public override string GetDisplayDateString(DateTime date)
 85             {
 86                 return date.ToString("yyyy-MM");
 87             }
 88
 89             public override IEnumerable<DateTime> SimulateDates(DateTime startDate, DateTime endDate)
 90             {
 91                 for (var i = startDate; i <= endDate; i = i.AddMonths(1))
 92                 {
 93                     yield return i;
 94                 }
 95             }
 96         }
 97
 98         private class DayCycleType : CycleType
 99         {
100             public override DateTime GetDefaultStartDate(DateTime endDate)
101             {
102                 return endDate.AddMonths(-1);
103             }
104
105             public override string GetDisplayDateString(DateTime date)
106             {
107                 return date.ToString("MM-dd");
108             }
109
110             public override IEnumerable<DateTime> SimulateDates(DateTime startDate, DateTime endDate)
111             {
112                 for (var i = startDate; i <= endDate; i = i.AddDays(1))
113                 {
114                     yield return i;
115                 }
116             }
117         }
118     }
119 }

备注返回目录

完成第一遍后，差点不想进行重构了，战胜自己非常不容易，继续努力。

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分类: Design Principle