策略模式

 策略模式的簡單實現

<?php
namespace  Strategy;

/**
 * 抽象算法類
 * @author struggle
 * @verison 2012-5-29
 */
abstract class Strategy {
    /**
     * 算法方法
     */
    public abstract function algorithmFunction();
}
/**
 * 具體算法類A
 * @author struggle
 * @verison 2012-5-29
 */
class SpecificStrategyA extends  Strategy {
    /**
     * 具體算法A的實現
     */
    public function algorithmFunction(){
        echo '具體算法A<br>';
    }
}
/**
 * 具體算法類B
 * @author struggle
 * @verison 2012-5-29
 */
class SpecificStrategyB extends Strategy {
    /**
     * 具體算法B的實現
     */
    public function algorithmFunction(){
        echo '具體算法B<br>';
    }
}
/**
 * 具體算法類C
 * @author struggle
 * @verison 2012-5-29
 */
class SpecificStrategyC extends  Strategy {
    /**
     * 具體算法c的實現
     */
    public function algorithmFunction() {
        echo '具體算法C<br>';
    }
}

class Context {
    /**
     * 算法對象
     * @var obj
     */
    private $Strategy ;
    /**
     * 設置算法對象
     * @param Strategy $obj
     */
    public function setStrategy( Strategy $obj){
        $this->Strategy = $obj;
    }

    public function contextInterface(){
        if(!isset($this->Strategy)){
           throw new  \Exception('算法對象未設置');
        }
        $this->Strategy->algorithmFunction();
    }
}

$context = new Context();
$context->setStrategy(new SpecificStrategyA());
$context->contextInterface();
$context->setStrategy(new SpecificStrategyB());
$context->contextInterface();
$context->setStrategy(new SpecificStrategyC());
$context->contextInterface();

---

#使用策略與簡單工廠的結合

Context類修改如下：

class Context{
    /**
     * 算法對象
     * @var obj
     */
    private $Strategy ;
    /**
     * 設置算法對象
     * @param $obj
     */
    public function __construct($type){
       switch (strtoupper($type)){ //全部轉換爲大寫
            case 'A':
                $this->Strategy = new SpecificStrategyA();
                break;
            case 'B':
                $this->Strategy = new SpecificStrategyB();
                break;
            case 'C':
                $this->Strategy = new SpecificStrategyC();
                break;
            default:
                throw new \Exception('未找到算法類 : '.$type);
       }
    }

    public function contextInterface(){
        if(!isset($this->Strategy)){
           throw new  \Exception('算法對象未設置');
        }
        $this->Strategy->algorithmFunction();
    }
}

$context = new Context('A');
$context->contextInterface();
$context = new Context('B');
$context->contextInterface();
$context = new Context('c');
$context->contextInterface();