此篇簡單介紹責任鍊模式.
使用情境:
在很多情況下, 例如網頁抓取往往會因為要抓取不同的標籤內文寫出不同的判斷. 若需求一直變動或者條件一直增加會導致需求變動時不易修改, 條件增加時要修改主程式. 這樣的結果往往會導致程式碼難以維護以及增加修改風險.
原理:
將每個判斷的條件轉換成物件, 並讓物件自身去判定自己有沒有需要, 若不需要則交由下一個物件.
類別圖 :
抽象類 :
namespace 責任鍊模式
{
/// <summary>
/// 由子類去判斷是否有需要處理, 不管子類需不需要執行最後都透過抽象類的方法來管理流程.
/// </summary>
abstract class AbstactMonkey
{
private AbstactMonkey _NextMonkey;
public AbstactMonkey(AbstactMonkey setMonkey)
{
this._NextMonkey = setMonkey;
}
// 開始在物件中尋找責任
public void DoSomething(DayOfWeek dayOfWeek)
{
if (this.isMyResponsibility(dayOfWeek)) // 請子類判斷是否是她的責任
{
this.MyAction(dayOfWeek);
Console.WriteLine("責任鏈結束");
}
else
{
Console.WriteLine("找尋N次");
if (this._NextMonkey != null) // 請下一個子類做判斷
this._NextMonkey.DoSomething(dayOfWeek);
else
Console.WriteLine("找無負責的物件");
}
}
protected abstract void MyAction(DayOfWeek dayOfWeek);
protected abstract bool isMyResponsibility(DayOfWeek dayOfWeek);
}
}
實作類 :
namespace 責任鍊模式
{
class MondayMonkey : AbstactMonkey
{
public MondayMonkey(AbstactMonkey setMonkey) : base(setMonkey)
{
}
protected override bool isMyResponsibility(DayOfWeek dayOfWeek)
{
if (dayOfWeek == DayOfWeek.Monday)
return true;
return false;
}
protected override void MyAction(DayOfWeek dayOfWeek)
{
Console.WriteLine("星期一的猴子: 星期一穿新衣");
}
}
class TuesdayMonkey : AbstactMonkey
{
public TuesdayMonkey(AbstactMonkey setMonkey) : base(setMonkey)
{
}
protected override bool isMyResponsibility(DayOfWeek dayOfWeek)
{
if (dayOfWeek == DayOfWeek.Tuesday)
return true;
return false;
}
protected override void MyAction(DayOfWeek dayOfWeek)
{
Console.WriteLine("星期二的猴子: 星期二穿新衣");
}
}
class WednesdayMonkey : AbstactMonkey
{
public WednesdayMonkey(AbstactMonkey setMonkey) : base(setMonkey)
{
}
protected override bool isMyResponsibility(DayOfWeek dayOfWeek)
{
if (dayOfWeek == DayOfWeek.Wednesday)
return true;
return false;
}
protected override void MyAction(DayOfWeek dayOfWeek)
{
Console.WriteLine("星期三的猴子: 星期三穿新衣");
}
}
class ThursdayMonkey : AbstactMonkey
{
public ThursdayMonkey(AbstactMonkey setMonkey) : base(setMonkey)
{
}
protected override bool isMyResponsibility(DayOfWeek dayOfWeek)
{
if (dayOfWeek == DayOfWeek.Thursday)
return true;
return false;
}
protected override void MyAction(DayOfWeek dayOfWeek)
{
Console.WriteLine("星期四的猴子: 星期四穿新衣");
}
}
class FridayMonkey : AbstactMonkey
{
public FridayMonkey(AbstactMonkey setMonkey) : base(setMonkey)
{
}
protected override bool isMyResponsibility(DayOfWeek dayOfWeek)
{
if (dayOfWeek == DayOfWeek.Friday)
return true;
return false;
}
protected override void MyAction(DayOfWeek dayOfWeek)
{
Console.WriteLine("星期五的猴子: 星期五穿新衣");
}
}
class SaturdayMonkey : AbstactMonkey
{
public SaturdayMonkey(AbstactMonkey setMonkey) : base(setMonkey)
{
}
protected override bool isMyResponsibility(DayOfWeek dayOfWeek)
{
if (dayOfWeek == DayOfWeek.Saturday)
return true;
return false;
}
protected override void MyAction(DayOfWeek dayOfWeek)
{
Console.WriteLine("星期六的猴子: 星期六穿新衣");
}
}
class SundayMonkey : AbstactMonkey
{
public SundayMonkey(AbstactMonkey setMonkey) : base(setMonkey)
{
}
protected override bool isMyResponsibility(DayOfWeek dayOfWeek)
{
if (dayOfWeek == DayOfWeek.Sunday)
return true;
return false;
}
protected override void MyAction(DayOfWeek dayOfWeek)
{
Console.WriteLine("星期日的猴子: 星期日穿新衣");
}
}
}
用戶端 :
namespace 責任鍊模式
{
class Program
{
static void Main(string[] args)
{
// 情境: 每天有不同的猴子會做一件事, 一個禮拜七天就有七隻猴子.
// 如果使用傳統的寫法正常會包在switch..case中. switch(today){ case Monday: do..; break; case ......}
var today = DayOfWeek.Friday;
// 將判斷的條件通通塞入, 最後一個條件建構參數須為null.
var monkey =new FridayMonkey(new MondayMonkey(new TuesdayMonkey(
new WednesdayMonkey(new SaturdayMonkey(new ThursdayMonkey(new SundayMonkey(null)))))));
monkey.DoSomething(today);
Console.Read();
}
}
}
結果顯示 :
多多指教!! 歡迎交流!!
你不知道自己不知道，那你會以為你知道
