PHP design pattern visitor (Visitor pattern)

Introduction: This is a detailed page of the PHP design mode visitor (visitor mode). It introduces PHP, related knowledge, skills, experience, and some PHP source code.

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1 <? PHP
2 /**
3 * visitor Mode
4 *
5 * indicates an operation that acts on each element in an object structure. You can define a new operation that acts on these elements without changing the classes of each element.
6 *
7 */
8 abstract class visitor
9 {
10 Abstract Public Function visitcroncreteelementa ($ element );
11 Abstract Public Function visitcroncreteelementb ($ element );
12}
13
14 class concretevisitor1 extends visitor
15 {
16 public function visitcroncreteelementa ($ element)
17 {
18 echo get_class ($ element). "Visit 1A <br/> ";
19}
20
21 public function visitcroncreteelementb ($ element)
22 {
23 echo get_class ($ element). "Visit 1B <br/> ";
24}
25}
26
27 class concretevisitor2 extends visitor
28 {
29 public function visitcroncreteelementa ($ element)
30 {
31 echo get_class ($ element). "Visit 2a <br/> ";
32}
33
34 public function visitcroncreteelementb ($ element)
35 {
36 echo get_class ($ element). "Visit 2B <br/> ";
37}
38}
39
40 abstract class Element
41 {
42 Abstract Public Function accept ($ visitor );
43}
44
45 class concreteelementa extends Element
46 {
47 Public Function accept ($ visitor)
48 {
49 $ visitor-> visitcroncreteelementa ($ this );
50}
51}
52
53 class concreteelementb extends Element
54 {
55 public function accept ($ visitor)
56 {
57 $ visitor-> visitcroncreteelementb ($ this );
58}
59}
60
61 class objectstructure
62 {
63 private $ _ elements = array ();
64
65 public function attach ($ element)
66 {
67 $ this-> _ elements [] = $ element;
68}
69
70 public function detach ($ element)
71 {
72 if ($ key = array_search ($ element, $ this-> _ elements )! = False) unset ($ this-> _ elements [$ key]);
73}
74
75 public function 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 );

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