php魔術(shù)方法： __get() 和 __set()的妙用

feiyang10086

php魔術(shù)方法： __get() 和 __set()的妙用

Php代碼

1. 1.<?php   
   
2. 2.class Post {   
   
3. 3.  private $title;   
   
4. 4.  private $content;   
   
5. 5.  private $author;   
   
6. 6.  private $comments;   
   
7. 7.  
   
8. 8.  private $_getters = array('title', 'content', 'author', 'comments');   
   
9. 9.  private $_setters = array('title', 'content', 'author');   
   
10. 10.     
    
11. 11.  public function __get($property) {   
    
12. 12.    if (in_array($property, $this->_setters)) {   
    
13. 13.      return $this->$property;   
    
14. 14.    }   
    
15. 15.    else if (method_exists($this, '_get_' . $property))   
    
16. 16.      return call_user_func(array($this, '_get_' . $property));   
    
17. 17.    else if (in_array($property, $this->_getters) OR method_exists($this, '_set_' . $property))   
    
18. 18.      throw new Exception('Property "' . $property . '" is write-only.');   
    
19. 19.    else  
    
20. 20.      throw new Exception('Property "' . $property . '" is not accessible.');   
    
21. 21.  }   
    
22. 22.  
    
23. 23.  public function __set($property, $value) {   
    
24. 24.    if (in_array($property, $this->_getters)) {   
    
25. 25.      $this->$property = $value;   
    
26. 26.    }   
    
27. 27.    else if (method_exists($this, '_set_' . $property))   
    
28. 28.      call_user_func(array($this, '_set_' . $property), $value);   
    
29. 29.    else if (in_array($property, $this->_setters) OR method_exists($this, '_get_' . $property))   
    
30. 30.      throw new Exception('Property "' . $property . '" is read-only.');   
    
31. 31.    else  
    
32. 32.      throw new Exception('Property "' . $property . '" is not accessible.');   
    
33. 33.  }   
    
34. 34.}   
    
35. 35.?>   
    
36. 36.  
    
37. 37.This way the variables in the $_getters array can be read from the outside and the variables in the $_setters array can be modified from the outside, like this:   
    
38. 38.  
    
39. 39.<?php   
    
40. 40.$post = new Post();   
    
41. 41.$post->title = 'Hello, World';   
    
42. 42.echo $post->title;   
    
43. 43.  
    
44. 44.// The following will throw an exception since $comments is read-only:   
    
45. 45.$post->comments = 23;   
    
46. 46.?>   
    
47. 47.  
    
48. 48.And in case you need a less generic getter or setter at some point, you can remove the variable from the $_getters or $_setters array and implement a method like:   
    
49. 49.  
    
50. 50.<?php   
    
51. 51.private function _set_title($value) {   
    
52. 52.  $this->title = str_replace('World', 'Universe', $value);   
    
53. 53.}   
    
54. 54.?>   
    
55. 55.  
    
56. 56.And from the outside the property could still be used with:   
    
57. 57.  
    
58. 58.<?php   
    
59. 59.$post->title = 'Hello, World!';   
    
60. 60.?>  
    
61. <?php
    
62. class Post {
    
63.   private $title;
    
64.   private $content;
    
65.   private $author;
    
66.   private $comments;
    
67. 
    
68.   private $_getters = array('title', 'content', 'author', 'comments');
    
69.   private $_setters = array('title', 'content', 'author');
    
70.   
    
71.   public function __get($property) {
    
72.     if (in_array($property, $this->_setters)) {
    
73.       return $this->$property;
    
74.     }
    
75.     else if (method_exists($this, '_get_' . $property))
    
76.       return call_user_func(array($this, '_get_' . $property));
    
77.     else if (in_array($property, $this->_getters) OR method_exists($this, '_set_' . $property))
    
78.       throw new Exception('Property "' . $property . '" is write-only.');
    
79.     else
    
80.       throw new Exception('Property "' . $property . '" is not accessible.');
    
81.   }
    
82. 
    
83.   public function __set($property, $value) {
    
84.     if (in_array($property, $this->_getters)) {
    
85.       $this->$property = $value;
    
86.     }
    
87.     else if (method_exists($this, '_set_' . $property))
    
88.       call_user_func(array($this, '_set_' . $property), $value);
    
89.     else if (in_array($property, $this->_setters) OR method_exists($this, '_get_' . $property))
    
90.       throw new Exception('Property "' . $property . '" is read-only.');
    
91.     else
    
92.       throw new Exception('Property "' . $property . '" is not accessible.');
    
93.   }
    
94. }
    
95. ?>
    
96. 
    
97. This way the variables in the $_getters array can be read from the outside and the variables in the $_setters array can be modified from the outside, like this:
    
98. 
    
99. <?php
    
100. $post = new Post();
     
101. $post->title = 'Hello, World';
     
102. echo $post->title;
     
103. 
     
104. // The following will throw an exception since $comments is read-only:
     
105. $post->comments = 23;
     
106. ?>
     
107. 
     
108. And in case you need a less generic getter or setter at some point, you can remove the variable from the $_getters or $_setters array and implement a method like:
     
109. 
     
110. <?php
     
111. private function _set_title($value) {
     
112.   $this->title = str_replace('World', 'Universe', $value);
     
113. }
     
114. ?>
     
115. 
     
116. And from the outside the property could still be used with:
     
117. 
     
118. <?php
     
119. $post->title = 'Hello, World!';
     
120. ?>

復(fù)制代碼

上面是手冊里的例子，但是我覺得應(yīng)該是先判斷類里面是否有處理屬性的方法，有的話就調(diào)用該方法，沒有就直接設(shè)置該屬性。

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