{"id":112,"date":"2008-03-08T13:42:13","date_gmt":"2008-03-08T13:42:13","guid":{"rendered":""},"modified":"2008-03-08T13:42:13","modified_gmt":"2008-03-08T13:42:13","slug":"112","status":"publish","type":"post","link":"https:\/\/www.poloo.org\/?p=112","title":{"rendered":"\u7b56\u7565\u6a21\u5f0f(Strategy Pattern)"},"content":{"rendered":"

\u4e00\u3001 \u7b56\u7565\uff08Strategy\uff09\u6a21\u5f0f
\u7b56\u7565\u6a21\u5f0f\u7684\u7528\u610f\u662f\u9488\u5bf9\u4e00\u7ec4\u7b97\u6cd5\uff0c\u5c06\u6bcf\u4e00\u4e2a\u7b97\u6cd5\u5c01\u88c5\u5230\u5177\u6709\u5171\u540c\u63a5\u53e3\u7684\u72ec\u7acb\u7684\u7c7b\u4e2d\uff0c\u4ece\u800c\u4f7f\u5f97\u5b83\u4eec\u53ef\u4ee5\u76f8\u4e92\u66ff\u6362\u3002\u7b56\u7565\u6a21\u5f0f\u4f7f\u5f97\u7b97\u6cd5\u53ef\u4ee5\u5728\u4e0d\u5f71\u54cd\u5230\u5ba2\u6237\u7aef\u7684\u60c5\u51b5\u4e0b\u53d1\u751f\u53d8\u5316\u3002<\/p>\n

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\u4e8c\u3001 \u7b56\u7565\u6a21\u5f0f\u7684\u7ed3\u6784
\u7b56\u7565\u6a21\u5f0f\u662f\u5bf9\u7b97\u6cd5\u7684\u5305\u88c5\uff0c\u662f\u628a\u4f7f\u7528\u7b97\u6cd5\u7684\u8d23\u4efb\u548c\u7b97\u6cd5\u672c\u8eab\u5206\u5272\u5f00\uff0c\u59d4\u6d3e\u7ed9\u4e0d\u540c\u7684\u5bf9\u8c61\u7ba1\u7406\u3002\u7b56\u7565\u6a21\u5f0f\u901a\u5e38\u628a\u4e00\u4e2a\u7cfb\u5217\u7684\u7b97\u6cd5\u5305\u88c5\u5230\u4e00\u7cfb\u5217\u7684\u7b56\u7565\u7c7b\u91cc\u9762\uff0c\u4f5c\u4e3a\u4e00\u4e2a\u62bd\u8c61\u7b56\u7565\u7c7b\u7684\u5b50\u7c7b\u3002\u7528\u4e00\u53e5\u8bdd\u6765\u8bf4\uff0c\u5c31\u662f\uff1a”\u51c6\u5907\u4e00\u7ec4\u7b97\u6cd5\uff0c\u5e76\u5c06\u6bcf\u4e00\u4e2a\u7b97\u6cd5\u5c01\u88c5\u8d77\u6765\uff0c\u4f7f\u5f97\u5b83\u4eec\u53ef\u4ee5\u4e92\u6362\u3002”<\/p>\n

\u7b56\u7565\u53c8\u79f0\u505a\u653f\u7b56\uff08Policy\uff09\u6a21\u5f0f\u3010GOF95\u3011\u3002\u4e0b\u9762\u662f\u4e00\u4e2a\u793a\u610f\u6027\u7684\u7b56\u7565\u6a21\u5f0f\u7ed3\u6784\u56fe\uff1a

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\u73af\u5883\uff08Context\uff09\u89d2\u8272\uff1a\u6301\u6709\u4e00\u4e2aStrategy\u7c7b\u7684\u5f15\u7528\u3002
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\u5177\u4f53\u7b56\u7565\uff08ConcreteStrategy\uff09\u89d2\u8272\uff1a\u5305\u88c5\u4e86\u76f8\u5173\u7684\u7b97\u6cd5\u6216\u884c\u4e3a\u3002 <\/p>\n

\u4e09\u3001 \u793a\u610f\u6027\u6e90\u4ee3\u7801<\/p>\n

\/\/ Strategy pattern -- Structural example  
using System;<\/p>\n

\/\/ \"Strategy\"
abstract class Strategy
{
  \/\/ Methods
  abstract public void AlgorithmInterface();
}<\/p>\n

\/\/ \"ConcreteStrategyA\"
class ConcreteStrategyA : Strategy
{
  \/\/ Methods
  override public void AlgorithmInterface()
  {
    Console.WriteLine(\"Called ConcreteStrategyA.AlgorithmInterface()\");
  }
}<\/p>\n

\/\/ \"ConcreteStrategyB\"
class ConcreteStrategyB : Strategy
{
  \/\/ Methods
  override public void AlgorithmInterface()
  {
    Console.WriteLine(\"Called ConcreteStrategyB.AlgorithmInterface()\");
  }
}<\/p>\n

\/\/ \"ConcreteStrategyC\"
class ConcreteStrategyC : Strategy
{
  \/\/ Methods
  override public void AlgorithmInterface()
  {
    Console.WriteLine(\"Called ConcreteStrategyC.AlgorithmInterface()\");
  }
}<\/p>\n

\/\/ \"Context\"
class Context
{
  \/\/ Fields
  Strategy strategy;<\/p>\n

  \/\/ Constructors
  public Context( Strategy strategy )
  {
    this.strategy = strategy;
  }<\/p>\n

  \/\/ Methods
  public void ContextInterface()
  {
    strategy.AlgorithmInterface();
  }
}<\/p>\n

\/**\/\/\/\/ <summary>
\/\/\/ Client test
\/\/\/ <\/summary>
public class Client
{
  public static void Main( string[] args )
  {
    \/\/ Three contexts following different strategies
    Context c = new Context( new ConcreteStrategyA() );
    c.ContextInterface();<\/p>\n

    Context d = new Context( new ConcreteStrategyB() );
    d.ContextInterface();<\/p>\n

    Context e = new Context( new ConcreteStrategyC() );
    e.ContextInterface();
  }
}
<\/code><\/p>\n

\u56db\u3001 \u4f55\u65f6\u4f7f\u7528\u4f55\u79cd\u5177\u4f53\u7b56\u7565\u89d2\u8272
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\/\/ Strategy pattern -- Real World example  
using System;
using System.Collections;<\/p>\n

\/\/ \"Strategy\"
abstract class SortStrategy
{
  \/\/ Methods
  abstract public void Sort( ArrayList list );
}<\/p>\n

\/\/ \"ConcreteStrategy\"
class QuickSort : SortStrategy
{
  \/\/ Methods
  public override void Sort(ArrayList list )
  {
    list.Sort(); \/\/ Default is Quicksort
    Console.WriteLine(\"QuickSorted list \");
  }
}<\/p>\n

\/\/ \"ConcreteStrategy\"
class ShellSort : SortStrategy
{
  \/\/ Methods
  public override void Sort(ArrayList list )
  {
    \/\/list.ShellSort();
    Console.WriteLine(\"ShellSorted list \");
  }
}<\/p>\n

\/\/ \"ConcreteStrategy\"
class MergeSort : SortStrategy
{
  \/\/ Methods
  public override void Sort( ArrayList list )
  {
    \/\/list.MergeSort();
    Console.WriteLine(\"MergeSorted list \");
  }
}<\/p>\n

\/\/ \"Context\"
class SortedList
{
  \/\/ Fields
  private ArrayList list = new ArrayList();
  private SortStrategy sortstrategy;<\/p>\n

  \/\/ Constructors
  public void SetSortStrategy( SortStrategy sortstrategy )
  {
    this.sortstrategy = sortstrategy;
  }<\/p>\n

  \/\/ Methods
  public void Sort()
  {
    sortstrategy.Sort( list );
  }<\/p>\n

  public void Add( string name )
  {
    list.Add( name );
  }<\/p>\n

  public void Display()
  {
    foreach( string name in list )
      Console.WriteLine( \" \" + name );
  }
}<\/p>\n

\/**\/\/\/\/ <summary>
\/\/\/ StrategyApp test
\/\/\/ <\/summary>
public class StrategyApp
{
  public static void Main( string[] args )
  {
    \/\/ Two contexts following different strategies
    SortedList studentRecords = new SortedList( );
    studentRecords.Add( \"Samual\" );
    studentRecords.Add( \"Jimmy\" );
    studentRecords.Add( \"Sandra\" );
    studentRecords.Add( \"Anna\" );
    studentRecords.Add( \"Vivek\" );<\/p>\n

    studentRecords.SetSortStrategy( new QuickSort() );
    studentRecords.Sort();
    studentRecords.Display();
  }
}
<\/code><\/p>\n

\u516d\u3001 \u5728\u4ec0\u4e48\u60c5\u51b5\u4e0b\u5e94\u5f53\u4f7f\u7528\u7b56\u7565\u6a21\u5f0f
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1. \u5982\u679c\u5728\u4e00\u4e2a\u7cfb\u7edf\u91cc\u9762\u6709\u8bb8\u591a\u7c7b\uff0c\u5b83\u4eec\u4e4b\u95f4\u7684\u533a\u522b\u4ec5\u5728\u4e8e\u5b83\u4eec\u7684\u884c\u4e3a\uff0c\u90a3\u4e48\u4f7f\u7528\u7b56\u7565\u6a21\u5f0f\u53ef\u4ee5\u52a8\u6001\u5730\u8ba9\u4e00\u4e2a\u5bf9\u8c61\u5728\u8bb8\u591a\u884c\u4e3a\u4e2d\u9009\u62e9\u4e00\u79cd\u884c\u4e3a\u3002<\/p>\n

2. \u4e00\u4e2a\u7cfb\u7edf\u9700\u8981\u52a8\u6001\u5730\u5728\u51e0\u79cd\u7b97\u6cd5\u4e2d\u9009\u62e9\u4e00\u79cd\u3002\u90a3\u4e48\u8fd9\u4e9b\u7b97\u6cd5\u53ef\u4ee5\u5305\u88c5\u5230\u4e00\u4e2a\u4e2a\u7684\u5177\u4f53\u7b97\u6cd5\u7c7b\u91cc\u9762\uff0c\u800c\u8fd9\u4e9b\u5177\u4f53\u7b97\u6cd5\u7c7b\u90fd\u662f\u4e00\u4e2a\u62bd\u8c61\u7b97\u6cd5\u7c7b\u7684\u5b50\u7c7b\u3002\u6362\u8a00\u4e4b\uff0c\u8fd9\u4e9b\u5177\u4f53\u7b97\u6cd5\u7c7b\u5747\u6709\u7edf\u4e00\u7684\u63a5\u53e3\uff0c\u7531\u4e8e\u591a\u6001\u6027\u539f\u5219\uff0c\u5ba2\u6237\u7aef\u53ef\u4ee5\u9009\u62e9\u4f7f\u7528\u4efb\u4f55\u4e00\u4e2a\u5177\u4f53\u7b97\u6cd5\u7c7b\uff0c\u5e76\u53ea\u6301\u6709\u4e00\u4e2a\u6570\u636e\u7c7b\u578b\u662f\u62bd\u8c61\u7b97\u6cd5\u7c7b\u7684\u5bf9\u8c61\u3002<\/p>\n

3. \u4e00\u4e2a\u7cfb\u7edf\u7684\u7b97\u6cd5\u4f7f\u7528\u7684\u6570\u636e\u4e0d\u53ef\u4ee5\u8ba9\u5ba2\u6237\u7aef\u77e5\u9053\u3002\u7b56\u7565\u6a21\u5f0f\u53ef\u4ee5\u907f\u514d\u8ba9\u5ba2\u6237\u7aef\u6d89\u53ca\u5230\u4e0d\u5fc5\u8981\u63a5\u89e6\u5230\u7684\u590d\u6742\u7684\u548c\u53ea\u4e0e\u7b97\u6cd5\u6709\u5173\u7684\u6570\u636e\u3002<\/p>\n

4. \u5982\u679c\u4e00\u4e2a\u5bf9\u8c61\u6709\u5f88\u591a\u7684\u884c\u4e3a\uff0c\u5982\u679c\u4e0d\u7528\u6070\u5f53\u7684\u6a21\u5f0f\uff0c\u8fd9\u4e9b\u884c\u4e3a\u5c31\u53ea\u597d\u4f7f\u7528\u591a\u91cd\u7684\u6761\u4ef6\u9009\u62e9\u8bed\u53e5\u6765\u5b9e\u73b0\u3002\u6b64\u65f6\uff0c\u4f7f\u7528\u7b56\u7565\u6a21\u5f0f\uff0c\u628a\u8fd9\u4e9b\u884c\u4e3a\u8f6c\u79fb\u5230\u76f8\u5e94\u7684\u5177\u4f53\u7b56\u7565\u7c7b\u91cc\u9762\uff0c\u5c31\u53ef\u4ee5\u907f\u514d\u4f7f\u7528\u96be\u4ee5\u7ef4\u62a4\u7684\u591a\u91cd\u6761\u4ef6\u9009\u62e9\u8bed\u53e5\uff0c\u5e76\u4f53\u73b0\u9762\u5411\u5bf9\u8c61\u8bbe\u8ba1\u7684\u6982\u5ff5\u3002<\/p>\n

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\u63a8\u8350\u5927\u5bb6\u8bfb\u4e00\u8bfb\u300aIoC \u5bb9\u5668\u548cDependency Injection \u6a21\u5f0f\u300b\uff0c\u4f5c\u8005Martin Fowler\u3002\u7f51\u4e0a\u53ef\u4ee5\u627e\u5230\u4e2d\u6587\u7248\u7684PDF\u6587\u4ef6\u3002\u4e3a\u7b56\u7565\u6a21\u5f0f\u7684\u5b9e\u65bd\u63d0\u4f9b\u4e86\u4e00\u4e2a\u975e\u5e38\u597d\u7684\u65b9\u6848\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"

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