[php]php设计模式 Visitor (访问者模式)

<?php
 2 /**
 3  * 访问者模式
 4  *
 5  * 表示一个作用于某对象结构中的各元素的操作,可以在不改变各元素的类的前提下定义作用于这些元素的新操作
 6  *
 7 */
 8 abstractclass Visitor
 9 {
10 abstractpublicfunction visitCroncreteElementA($element);
11 abstractpublicfunction visitCroncreteElementB($element);
12 }
13 
14 class ConcreteVisitor1 extends Visitor
15 {
16 publicfunction visitCroncreteElementA($element)
17     {
18 echoget_class($element)." visit 1A<br/>";
19     }
20 
21 publicfunction visitCroncreteElementB($element)
22     {
23 echoget_class($element)." visit 1B<br/>";
24     } 
25 }
26 
27 class ConcreteVisitor2 extends Visitor
28 {
29 publicfunction visitCroncreteElementA($element)
30     {
31 echoget_class($element)." visit 2A<br/>";
32     }
33 
34 publicfunction visitCroncreteElementB($element)
35     {
36 echoget_class($element)." visit 2B<br/>";
37     } 
38 }
39 
40 abstractclass Element
41 {
42 abstractpublicfunction accept($visitor); 
43 }
44 
45 class ConcreteElementA extends Element
46 {
47 publicfunction accept($visitor)
48     {
49 $visitor->visitCroncreteElementA($this);
50     }
51 }
52 
53 class ConcreteElementB extends Element
54 {
55 publicfunction accept($visitor)
56     {
57 $visitor->visitCroncreteElementB($this);
58     }
59 }
60 
61 class ObjectStructure
62 {
63 private$_elements=array();
64 
65 publicfunction attach($element)
66     {
67 $this->_elements[] =$element;
68     }
69 
70 publicfunction detach($element)
71     {
72 if($key=array_search($element,$this->_elements) !==false) unset($this->_elements[$key]);
73     }
74 
75 publicfunction accept($visitor)
76     {
77 foreach($this->_elements as$element)
78         {
79 $element->accept($visitor);
80         }
81     }
82 }
83 
84 //
85 $objOS=new ObjectStructure();
86 $objOS->attach(new ConcreteElementA());
87 $objOS->attach(new ConcreteElementB());
88 
89 $objCV1=new ConcreteVisitor1();
90 $objCV2=new ConcreteVisitor2();
91 
92 $objOS->accept($objCV1);
93 $objOS->accept($objCV2);