PHP设计模式之调解者模式的深入解析

php  /  管理员 发布于 7年前   137

        /** 
     * AbstractColleague. 
     */ 
    interface Filter 
    { 
 public function filter($value); 
    } 

    /** 
     * Colleague. We decide in the implementation phase 
     * that Colleagues should not know the next Colleague 
     * in the chain, resorting to a Mediator to link them together. 
     * This choice succesfully avoids a base abstract class 
     * for Filters. 
     * Remember that this is an example: it is not only 
     * Chain of Responsibility that can be alternatively implemented 
     * as a Mediator. 
     */ 
    class TrimFilter implements Filter 
    { 
  public function filter($value) 
  { 
      return trim($value); 
  } 
    }

    /**  
     * Colleague.  
     */  
    class NullFilter implements Filter  
    {  
 public function filter($value)  
 {  
     return $value ? $value : '';  
 }  
    }  
    /**  
     * Colleague.  
     */  
    class HtmlEntitiesFilter implements Filter  
    {  
 public function filter($value)  
 {  
     return htmlentities($value);  
 }  
    }

    /**  
     * The Mediator. We avoid referencing it from ConcreteColleagues  
     * and so the need for an interface. We leave the implementation  
     * of a bidirectional channel for the Observer pattern's example.  
     * This class responsibility is to store the value and coordinate  
     * filters computation when they have to be applied to the value.  
     * Filtering responsibilities are obviously a concern of  
     * the Colleagues, which are Filter implementations.  
     */  
    class InputElement  
    {  
 protected $_filters;  
 protected $_value;  
 public function addFilter(Filter $filter)  
 {  
     $this->_filters[] = $filter;  
     return $this;  
 }  
 public function setValue($value)  
 {  
     $this->_value = $this->_filter($value);  
 }  
 protected function _filter($value)  
 {  
     foreach ($this->_filters as $filter) {  
  $value = $filter->filter($value);  
     }  
     return $value;  
 }  
 public function getValue()  
 {  
     return $this->_value;  
 }    
    }  
    $input = new InputElement();  
    $input->addFilter(new NullFilter())  
   ->addFilter(new TrimFilter())  
   ->addFilter(new HtmlEntitiesFilter());  
    $input->setValue(' You should use the 
-
 tags for your headings.');  
    echo $input->getValue(), "\n";