PHP设计模式之调解者模式的深入解析

    <?php
    / 
     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 suesfully 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); 
  } 
    } <PRE class=php name="code">    / 
     Colleague. 
     / 
    class NullFilter implements Filter 
    { 
 public function filter($value) 
 { 
     return $value ? $value : ''; 
 } 
    } 

    / 
     Colleague. 
     / 
    class HtmlEntitiesFilter implements Filter 
    { 
 public function filter($value) 
 { 
     return htmlentities($value); 
 } 
    }
</PRE><PRE class=php name="code">    / 
     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 putation 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 <h1>-<h6> tags for your headings.'); 
    echo $input->getValue(), "\n";
</PRE>
<PRE></PRE>