過濾器模式

　　過濾器模式（Filter Pattern）或標準模式（Criteria Pattern）是一種設計模式，這種模式允許開發人員使用不同的標準來過濾一組對象，通過邏輯運算以解耦的方式把它們連接起來。這種類型的設計模式屬於結構型模式，它結合多個標準來獲得單一標準。

　　故名思意，就是將原始數據經過不同規則的篩選得到想要的數據。

　　角色：1）待過濾數據類；2）過濾器；3）邏輯過濾器；4）使用者

　　最近在找工作，這真是一個活生生被過濾的例子啊。於是以找工作，和公司各種過濾條件為例，詳見代碼（php版本）：

  1 <?php
  2 /*
  3  * 過濾器方法模式示例
 
  4  */
  5 
  6 preg_match("/cli/i", php_sapi_name()) ? define(‘LINE_BREAK‘, PHP_EOL) : define(‘LINE_BREAK‘, "<br/>");
  7 
  8 /*
  9  * 角色：待過濾數據類
 10  * 找工作者
 11  */
 12 class JobSeeker
 13 {
 14     private $_name;
 15     private $_age;
 16     private $_sex;
 17     private $_working_years
 
;
 18     private $_skills;
 19     
 20     public function __construct($name,$age,$sex,$working_years,$skills) {
 21         $this->_name = $name;
 22         $this->_age = $age;
 23         $this->_sex = $sex;
 24         $this->_working_years = $working_years;
 25         $this
 
->_skills = $skills;
 26     }
 27 
 28     public function getName(){
 29         return $this->_name;
 30     }    
 31     public function getAge(){
 32         return $this->_age;
 33     }
 34     public function getSex(){
 35         return $this->_sex;
 36     }
 37     public function getWorkingYears(){
 38         return $this->_working_years;
 39     }
 40     public function getSkills(){
 41         return $this->_skills;
 42     }    
 43 }
 44 
 45 
 46 /*
 47  *用來過濾的接口類 
 48  */
 49 interface Criteria{
 50     public function meetCriteria( $job_seekers);
 51 } 
 52 
 53 /*
 54  * 角色：過濾器
 55  * 只需要男性的過濾類
 56  */
 57 
 58 class CriteriaMale implements Criteria{
 59     public function meetCriteria( $job_seekers) {
 60         if(empty($job_seekers))
 61             return null;
 62         $job_seekers_criteria_male = array();
 63         foreach($job_seekers as $job_seeker){
 64             if($job_seeker->getSex() == "male")
 65                 $job_seekers_criteria_male[] = $job_seeker;
 66         }
 67         return $job_seekers_criteria_male;
 68     }
 69 }
 70 
 71 /*
 72  * 角色：過濾器
 73  * 年齡區間的過濾器
 74  */
 75 class CriteriaAge implements Criteria{
 76     private $_min = 18;
 77     private $_max;
 78     public function __construct($min,$max) {
 79         $this->_min = $min;
 80         $this->_max = $max;
 81     }
 82     public function meetCriteria( $job_seekers){
 83         $job_seekers_criteria_age = array();
 84         foreach($job_seekers as $job_seek){
 85             $age = $job_seek->getAge();
 86             if(is_int($age) && $age >= $this->_min && $age <= $this->_max){
 87                 $job_seekers_criteria_age[] = $job_seek;
 88             }
 89         }
 90         return $job_seekers_criteria_age;
 91     }
 92 }
 93 
 94 /*
 95  * 角色：邏輯過濾器
 96  * AND過濾器
 97  */
 98 class CriteriaAnd implements Criteria{
 99     private $_criteria;
100     private $_another_criteria;
101     
102     public function __construct($criteria,$another_criteria) {
103         $this->_criteria = $criteria;
104         $this->_another_criteria = $another_criteria;
105     }
106     public function meetCriteria( $job_seekers) {
107         $firstCriteriaPersons = $this->_criteria->meetCriteria($job_seekers);
108         return $this->_another_criteria->meetCriteria($firstCriteriaPersons);
109     }
110 }
111 
112 /*
113  * 打印篩選後人資料，與設計模式無關
114  */
115 function printPerson($job_seekers){
116     if(empty($job_seekers)){
117         echo "".LINE_BREAK;return;
118     }
119     foreach($job_seekers as $job_seeker){
120         printf("Person : [ Name : %s , Age : %s , Sex : %s , Working Years : %s , Skills : %s ]".LINE_BREAK,$job_seeker->getName(),$job_seeker->getAge(),$job_seeker->getSex(),$job_seeker->getWorkingYears(),$job_seeker->getSkills());
121     }
122     
123 }
124 /*
125  * 角色：使用者
126  * 實際中就是HR。。。
127  */
128 $job_seekers = array();
129 $job_seekers[] = new JobSeeker("xiao wang", 31, "male", 8, "php");
130 $job_seekers[] = new JobSeeker("xiao li", 25, "male", 2, "java");
131 $job_seekers[] = new JobSeeker("xiao zhan", 26, "female", 3, "test");
132 $job_seekers[] = new JobSeeker("xiao huang", 28, "male", 4, "python");
133 $job_seekers[] = new JobSeeker("xiao huang", 22, "male", 0, "c");
134 
135 $male = new CriteriaMale();
136 $age_under_30 = new CriteriaAge(18,30);
137 $male_and_age_under_30 = new CriteriaAnd($male,$age_under_30);
138 
139 echo "Males:".LINE_BREAK;
140 printPerson($male->meetCriteria($job_seekers));
141 echo "Age Under 30:".LINE_BREAK;
142 printPerson($age_under_30->meetCriteria($job_seekers));
143 echo "Males And Age Under 30:".LINE_BREAK;
144 printPerson($male_and_age_under_30->meetCriteria($job_seekers));
145 /*
146  Males:
147 Person : [ Name : xiao wang , Age : 31 , Sex : male , Working Years : 8 , Skills : php ]
148 Person : [ Name : xiao li , Age : 25 , Sex : male , Working Years : 2 , Skills : java ]
149 Person : [ Name : xiao huang , Age : 28 , Sex : male , Working Years : 4 , Skills : python ]
150 Person : [ Name : xiao huang , Age : 22 , Sex : male , Working Years : 0 , Skills : c ]
151 Age Under 30:
152 Person : [ Name : xiao li , Age : 25 , Sex : male , Working Years : 2 , Skills : java ]
153 Person : [ Name : xiao zhan , Age : 26 , Sex : female , Working Years : 3 , Skills : test ]
154 Person : [ Name : xiao huang , Age : 28 , Sex : male , Working Years : 4 , Skills : python ]
155 Person : [ Name : xiao huang , Age : 22 , Sex : male , Working Years : 0 , Skills : c ]
156 Males And Age Under 30:
157 Person : [ Name : xiao li , Age : 25 , Sex : male , Working Years : 2 , Skills : java ]
158 Person : [ Name : xiao huang , Age : 28 , Sex : male , Working Years : 4 , Skills : python ]
159 Person : [ Name : xiao huang , Age : 22 , Sex : male , Working Years : 0 , Skills : c ]
160  */

　　第一個是過濾只要男性，第二個是過濾只要30歲以下的，第三個過濾是只要男性和30歲以下的。

參考資料：

設計模式學習系列——過濾器模式