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HomeBackend DevelopmentPHP Tutorial学习php设计模式 php实现策略模式(strategy)_PHP

一、意图
定义一系列的算法,把它们一个个封装起来,并且使它们可相互替换。策略模式可以使算法可独立于使用它的客户而变化
策略模式变化的是算法
二、策略模式结构图

三、策略模式中主要角色
抽象策略(Strategy)角色:定义所有支持的算法的公共接口。通常是以一个接口或抽象来实现。Context使用这个接口来调用其ConcreteStrategy定义的算法
具体策略(ConcreteStrategy)角色:以Strategy接口实现某具体算法
环境(Context)角色:持有一个Strategy类的引用,用一个ConcreteStrategy对象来配置
四、策略模式的优点和缺点
策略模式的优点:
1、策略模式提供了管理相关的算法族的办法
2、策略模式提供了可以替换继承关系的办法 将算封闭在独立的Strategy类中使得你可以独立于其Context改变它
3、使用策略模式可以避免使用多重条件转移语句。
策略模式的缺点:
1、客户必须了解所有的策略 这是策略模式一个潜在的缺点
2、Strategy和Context之间的通信开销
3、策略模式会造成很多的策略类
五、策略模式适用场景
1、许多相关的类仅仅是行为有异。“策略”提供了一种用多个行为中的一个行为来配置一个类的方法
2、需要使用一个算法的不同变体。
3、算法使用客户不应该知道的数据。可使用策略模式以避免暴露复杂的,与算法相关的数据结构
4、一个类定义了多种行为,并且 这些行为在这个类的操作中以多个形式出现。将相关的条件分支移和它们各自的Strategy类中以代替这些条件语句
六、策略模式与其它模式
Template模式:模板方法模式与策略模式的不同在于,策略模式使用委派的方法提供不同的算法行为,而模板方法使用继承的方法提供不同的算法行为
享元模式(flyweight模式):如果有多个客户端对象需要调用 同样的一睦策略类的话,就可以使它们实现享元模式
七、策略模式PHP示例

<&#63;php
/**
 * 抽象策略角色,以接口实现
 */
interface Strategy {
 
  /**
   * 算法接口
   */
  public function algorithmInterface();
}
 
/**
 * 具体策略角色A
 */
class ConcreteStrategyA implements Strategy {
 
  public function algorithmInterface() {
    echo 'algorithmInterface A<br />';
  }
}
 
/**
 * 具体策略角色B
 */
class ConcreteStrategyB implements Strategy {
 
  public function algorithmInterface() {
    echo 'algorithmInterface B<br />';
  }
}
 
/**
 * 具体策略角色C
 */
class ConcreteStrategyC implements Strategy {
 
  public function algorithmInterface() {
    echo 'algorithmInterface C<br />';
  }
}
 
/**
 * 环境角色
 */
class Context {
  /* 引用的策略 */
  private $_strategy;
 
  public function __construct(Strategy $strategy) {
    $this->_strategy = $strategy;
  }
 
  public function contextInterface() {
    $this->_strategy->algorithmInterface();
  }
 
}
 
/**
 * 客户端
 */
class Client {
 
  /**
   * Main program.
   */
  public static function main() {
    $strategyA = new ConcreteStrategyA();
    $context = new Context($strategyA);
    $context->contextInterface();
 
    $strategyB = new ConcreteStrategyB();
    $context = new Context($strategyB);
    $context->contextInterface();
 
    $strategyC = new ConcreteStrategyC();
    $context = new Context($strategyC);
    $context->contextInterface();
  }
 
}
 
Client::main();
&#63;>

以上就是使用php实现策略模式的代码,还有一些关于策略模式的概念区分,希望对大家的学习有所帮助。

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