【过滤器设计模式详解】C/Java/JS/Go/Python/TS不同语言实现
简介
过滤器模式（Filter Pattern）或标准模式（Criteria Pattern），是一种结构型模式。这种模式允许使用不同的标准条件来过滤一组对象，并通过逻辑运算的方式把各条件连接起来，它结合多个标准来获得单一标准。
例子将创建一个 Person 对象、Criteria 接口和实现了该接口的实体类，来过滤 Person 对象的列表。Test 类使用 Criteria 对象，基于各种标准和它们的结合来过滤 Person 对象的列表。
作用
- 可以通过层层筛选，过滤出自己想要的结果。
- 面向接口编程，将对象过滤，接口不依赖对象；对象无入侵，每次只需要增加规则就行了，不用修改过滤对象类。
实现步骤
- 创建Criteria基础接口，定义过滤方法。
- 创建多个条件类，实现过滤逻辑。
- 客户端调用时，通条件类过滤数据。
UML
Java代码
标准接口类
// Criteria.java 定义抽象标准接口，聚合实体对象 public interface Criteria { public List<Person> filter(List<Person> persons); }
具体标准实现类
// AndCriteria.java 定义And过滤标准 public class AndCriteria implements Criteria { private Criteria criteria; private Criteria otherCriteria; public AndCriteria(Criteria criteria, Criteria otherCriteria) { this.criteria = criteria; this.otherCriteria = otherCriteria; } @Override public List<Person> filter(List<Person> persons) { List<Person> firstCriteriaPersons = criteria.filter(persons); return otherCriteria.filter(firstCriteriaPersons); } } // OrCriteria.java 定义Or过滤标准 public class OrCriteria implements Criteria { private Criteria criteria; private Criteria otherCriteria; public OrCriteria(Criteria criteria, Criteria otherCriteria) { this.criteria = criteria; this.otherCriteria = otherCriteria; } @Override public List<Person> filter(List<Person> persons) { List<Person> firstCriteriaItems = criteria.filter(persons); List<Person> otherCriteriaItems = otherCriteria.filter(persons); for (Person person : otherCriteriaItems) { if (!firstCriteriaItems.contains(person)) { firstCriteriaItems.add(person); } } return firstCriteriaItems; } } // CriteriaFemale.java 根据标准接口实现的过滤 public class CriteriaFemale implements Criteria { @Override public List<Person> filter(List<Person> persons) { List<Person> femalePersons = new ArrayList<Person>(); for (Person person : persons) { if (person.getGender().equalsIgnoreCase("FEMALE")) { femalePersons.add(person); } } return femalePersons; } } // CriteriaMale.java 根据标准接口实现的过滤 public class CriteriaMale implements Criteria { @Override public List<Person> filter(List<Person> persons) { List<Person> malePersons = new ArrayList<Person>(); for (Person person : persons) { if (person.getGender().equalsIgnoreCase("MALE")) { malePersons.add(person); } } return malePersons; } } // CriteriaSingle.java 根据标准接口实现按属性的过滤 public class CriteriaSingle implements Criteria { @Override public List<Person> filter(List<Person> persons) { List<Person> singlePersons = new ArrayList<Person>(); for (Person person : persons) { if (person.getStatus().equalsIgnoreCase("SINGLE")) { singlePersons.add(person); } } return singlePersons; } }
业务实体类
// Person.java 定义一个实体类，用来过滤的对象 public class Person { private String name; private String gender; private String status; public Person(String name, String gender, String status) { this.name = name; this.gender = gender; this.status = status; } public String getName() { return name; } public String getGender() { return gender; } public String getStatus() { return status; } public String toString() { return "Person : [ Name : " + getName() + ", Gender : " + getGender() + ", Marital Status : " + getStatus() + " ]"; } }
测试调用
/** * 过滤器模式就是不断组合过滤条件，然后层层过滤的模式 * 这里是简单演示，用List筛选来模拟过滤，实际例子有各种数据结构 */ List<Person> persons = new ArrayList<Person>(); persons.add(new Person("王男单", "Male", "Single")); persons.add(new Person("李男婚", "Male", "Married")); persons.add(new Person("张女婚", "Female", "Married")); persons.add(new Person("赵女单", "Female", "Single")); persons.add(new Person("刘男单", "Male", "Single")); persons.add(new Person("杨男单", "Male", "Single")); Criteria male = new CriteriaMale(); Criteria female = new CriteriaFemale(); Criteria single = new CriteriaSingle(); Criteria singleMale = new AndCriteria(single, male); Criteria singleOrFemale = new OrCriteria(single, female); // 查询男性 System.out.println("Males: "); printPersons(male.filter(persons)); // 查询女性 System.out.println("\nFemales: "); printPersons(female.filter(persons)); // 嵌套查询女性且单身 System.out.println("\nFemales and Single: "); printPersons(single.filter(female.filter(persons))); // 查询男性男性单身 System.out.println("\nSingle Males: "); printPersons(singleMale.filter(persons)); // 查询女性或单身 System.out.println("\nSingle Or Females: "); printPersons(singleOrFemale.filter(persons));
C代码
head文件
// func.h文件 #include <stdio.h> #include <ctype.h> #include <stdlib.h> #include <stdbool.h> #include <string.h> char *str_toupper(char str[]); char *str_tolower(char str[]); // 定义用于过滤的Person数组查询对象 // 因C语言无法定义动态数组，将数组长度存在此处 typedef struct FilterPersons { int length; struct Person **persons; } FilterPersons; // 定义一个实体类，用来过滤的对象 typedef struct Person { char name[50]; char gender[20]; char status[20]; char *(*get_name)(struct Person *); char *(*to_string)(struct Person *); bool (*is_contained)(struct Person *, struct FilterPersons *); } Person; Person *person_constructor(char *name, char *gender, char *status); // 定义抽象标准接口，聚合要过滤的对象集合 typedef struct Criteria { struct Criteria *first_criteria; struct Criteria *other_criteria; FilterPersons *(*filter)(FilterPersons *, struct Criteria *); } Criteria; // 根据标准接口实现的过滤 typedef struct CriteriaFemale { FilterPersons *(*filter)(FilterPersons *, struct Criteria *); } CriteriaFemale; CriteriaFemale *criteria_female_constructor(); // 根据标准接口实现的过滤 typedef struct CriteriaMale { FilterPersons *(*filter)(FilterPersons *, struct Criteria *); } CriteriaMale; CriteriaMale *criteria_male_constructor(); // 根据标准接口实现的过滤 typedef struct CriteriaSingle { FilterPersons *(*filter)(FilterPersons *, struct Criteria *); } CriteriaSingle; CriteriaSingle *criteria_single_constructor(); // 定义And过滤标准 typedef struct AndCriteria { struct Criteria *first_criteria; struct Criteria *other_criteria; FilterPersons *(*filter)(FilterPersons *, struct Criteria *); } AndCriteria; AndCriteria *and_criteria_constructor(Criteria *, Criteria *); // 定义Or过滤标准 typedef struct OrCriteria { struct Criteria *first_criteria; struct Criteria *other_criteria; FilterPersons *(*filter)(FilterPersons *, struct Criteria *); } OrCriteria; OrCriteria *or_criteria_constructor(Criteria *, Criteria *);
条件接口类
// criteria.c 定义抽象标准接口，聚合实体对象 #include "func.h" // c语言没有抽象类或接口，Criterial作为基础struct定义在head， 这里放一些公共函数 char *str_toupper(char str[]) { int size = strlen(str); char *result = (char *)malloc(size * sizeof(char)); int i = 0; while (str[i]) { result[i] = toupper(str[i]); i++; } return result; } char *str_tolower(char str[]) { int size = strlen(str); char *result = (char *)malloc(size * sizeof(char)); int i = 0; while (str[i]) { result[i] = tolower(str[i]); i++; } return result; }
具体标准实现类
// and_criteria.c 定义And过滤标准 #include "func.h" // 先过滤条件1，再把结果按照条件2进行过滤 FilterPersons *and_criteria_filter(FilterPersons *filter, Criteria *criteria) { FilterPersons *first_filter = criteria->first_criteria->filter(filter, criteria); return criteria->other_criteria->filter(first_filter, criteria); } AndCriteria *and_criteria_constructor(Criteria *first_criteria, Criteria *other_criteria) { Criteria *criteria = (Criteria *)malloc(sizeof(Criteria)); criteria->filter = &and_criteria_filter; AndCriteria *and_criteria = (AndCriteria *)criteria; and_criteria->first_criteria = first_criteria; and_criteria->other_criteria = other_criteria; and_criteria->filter = &and_criteria_filter; return and_criteria; } // or_criteria.c 定义Or过滤标准 #include "func.h" // 先过滤条件1，再把结果按照条件2进行过滤 FilterPersons *or_criteria_filter(FilterPersons *filter, Criteria *criteria) { FilterPersons *first_filter = criteria->first_criteria->filter(filter, criteria); FilterPersons *other_filter = criteria->other_criteria->filter(filter, criteria); int first_size = first_filter->length; int other_size = other_filter->length; for (int i = 0; i < other_size; i++) { Person *person = other_filter->persons[i]; // 符合项如果不存在条件1里，则追加到条件1里去 if (!person->is_contained(person, first_filter)) { // 这里数组长度直接增加 first_filter->persons[first_size++] = person; } } first_filter->length = first_size; return first_filter; } OrCriteria *or_criteria_constructor(Criteria *first_criteria, Criteria *other_criteria) { Criteria *criteria = (Criteria *)malloc(sizeof(Criteria)); criteria->filter = &or_criteria_filter; OrCriteria *or_criteria = (OrCriteria *)criteria; or_criteria->first_criteria = first_criteria; or_criteria->other_criteria = other_criteria; or_criteria->filter = &or_criteria_filter; return or_criteria; } // ccriteria_female.c 根据标准接口实现的过滤 #include "func.h" // 根据是否女性进行过滤 FilterPersons *criteria_female_filter(FilterPersons *filter, Criteria *criteria) { int person_size = filter->length; int *female_index_list = (int *)malloc(person_size * sizeof(int)); int count = 0; char *gender; for (int i = 0; i < person_size; i++) { if (filter->persons[i] == NULL) { break; } gender = str_toupper(filter->persons[i]->gender); if (strcmp(gender, "FEMALE") == 0) { // 记录下所有符合条件的person下标 female_index_list[count] = i; count += 1; } } free(gender); free(female_index_list); // 将符合条件的person追加到新数组 Person **female_persons = (Person **)calloc(count, sizeof(Person)); for (int i = 0; i < count; i++) { female_persons[i] = filter->persons[female_index_list[i]]; } FilterPersons *female_filter = (FilterPersons *)calloc(1, sizeof(FilterPersons)); female_filter->length = count; female_filter->persons = female_persons; return female_filter; } CriteriaFemale *criteria_female_constructor() { Criteria *criteria = (Criteria *)malloc(sizeof(Criteria)); criteria->filter = &criteria_female_filter; CriteriaFemale *criteria_female = (CriteriaFemale *)criteria; criteria_female->filter = &criteria_female_filter; return criteria_female; } // criteria_male.c 根据标准接口实现的过滤 #include "func.h" // 根据是否男性进行过滤 FilterPersons *criteria_male_filter(FilterPersons *filter, Criteria *criteria) { int person_size = filter->length; int *male_index_list = (int *)malloc(person_size * sizeof(int)); int count = 0; char *gender; for (int i = 0; i < person_size; i++) { if (filter->persons[i] == NULL) { break; } gender = str_tolower(filter->persons[i]->gender); if (strcmp(gender, "male") == 0) { // 记录下所有符合条件的person下标 male_index_list[count] = i; count += 1; } } free(gender); free(male_index_list); // 将符合条件的person追加到新数组 Person **male_persons = (Person **)calloc(count, sizeof(Person)); for (int i = 0; i < count; i++) { male_persons[i] = filter->persons[male_index_list[i]]; } FilterPersons *male_filter = (FilterPersons *)calloc(1, sizeof(FilterPersons)); male_filter->length = count; male_filter->persons = male_persons; return male_filter; } CriteriaMale *criteria_male_constructor() { Criteria *criteria = (Criteria *)malloc(sizeof(Criteria)); criteria->filter = &criteria_male_filter; CriteriaMale *criteria_male = (CriteriaMale *)criteria; criteria_male->filter = &criteria_male_filter; return criteria_male; } // criteria_single.c 根据标准接口实现按属性的过滤 #include "func.h" // 根据是否单身进行过滤 FilterPersons *criteria_single_filter(FilterPersons *filter, Criteria *criteria) { int person_size = filter->length; int *single_index_list = (int *)malloc(person_size * sizeof(int)); int count = 0; char *status; for (int i = 0; i < person_size; i++) { if (filter->persons[i] == NULL) { break; } status = str_tolower(filter->persons[i]->status); if (strcmp(status, "single") == 0) { // 记录下所有符合条件的person下标 single_index_list[count] = i; count += 1; } } free(status); free(single_index_list); // 将符合条件的person追加到新数组 Person **single_persons = (Person **)calloc(count, sizeof(Person)); for (int i = 0; i < count; i++) { single_persons[i] = filter->persons[single_index_list[i]]; } FilterPersons *single_filter = (FilterPersons *)calloc(1, sizeof(FilterPersons)); single_filter->length = count; single_filter->persons = single_persons; return single_filter; } CriteriaSingle *criteria_single_constructor() { Criteria *criteria = (Criteria *)malloc(sizeof(Criteria)); criteria->filter = &criteria_single_filter; CriteriaSingle *criteria_single = (CriteriaSingle *)criteria; criteria_single->filter = &criteria_single_filter; return criteria_single; }
业务实体类
// person.c 定义一个实体类，用来过滤的对象 #include "func.h" // 是否被包含在对象数组中 bool person_is_contained(Person *person, FilterPersons *filter) { int persons_size = filter->length; for (int i = 0; i < persons_size; i++) { if (filter->persons[i] == person) { return true; } } return false; } char *person_get_name(Person *person) { return person->name; } // 返回字符串 char *person_to_string(Person *person) { char *result = (char *)malloc(500 * sizeof(char)); strcat(result, "Person :[ name :"); strcat(result, person->name); strcat(result, ", gender : "); strcat(result, person->gender); strcat(result, ", status : "); strcat(result, person->status); strcat(result, "]"); return result; } Person *person_constructor(char *name, char *gender, char *status) { Person *person = (Person *)malloc(sizeof(Person)); strncpy(person->name, name, 50); strncpy(person->gender, gender, 20); strncpy(person->status, status, 20); person->get_name = &person_get_name; person->to_string = &person_to_string; person->is_contained = &person_is_contained; return person; }
测试调用
/**
* 过滤器模式就是不断组合过滤条件，然后层层过滤的模式
* 这里是简单演示，用List筛选来模拟过滤，实际例子有各种数据结构。
*/
int data_size = 6;
// 定义一些数据
char data[6][3][100] = {
{"王男单", "Male", "Single"},
{"李男婚", "Male", "Married"},
{"张女婚", "Female", "Married"},
{"赵女单", "Female", "Single"},
{"刘男单", "Male", "Single"},
{"杨男单", "Male", "Single"}};
// 定义persons数组
Person *persons[data_size];
for (int i = 0; i < data_size; i++)
{
char *name = data[i][0];
char *gender = data[i][1];
char *status = data[i][2];
Person *person = person_constructor(name, gender, status);
persons[i] = person;
}
// 构建查询对象
FilterPersons *filter_persons = (FilterPersons *)malloc(sizeof(FilterPersons *));
filter_persons->length = data_size;
filter_persons->persons = persons;
// 声明属性过滤条件，可用Criteria或具体条件声明
Criteria *criteria_male = (Criteria *)criteria_male_constructor();
CriteriaFemale *criteria_female = criteria_female_constructor();
Criteria *criteria_single = (Criteria *)criteria_single_constructor();
// 声明逻辑条件，传入属性过滤条件
Criteria *single_male = (Criteria *)and_criteria_constructor(criteria_single, criteria_male);
OrCriteria *single_or_female = or_criteria_constructor(criteria_single, (Criteria *)criteria_female);
// 查询男性
printf("\n Males: ");
print_persons(((CriteriaMale *)criteria_male)->filter(filter_persons, criteria_male));
// 查询女性
printf("\nFemales: ");
print_persons(criteria_female->filter(filter_persons, (Criteria *)criteria_female));
// 嵌套查询女性且单身
printf("\nFemales and Single: ");
FilterPersons *females = criteria_female->filter(filter_persons, (Criteria *)criteria_female);
print_persons(((CriteriaSingle *)criteria_single)->filter(females, criteria_single));
// 查询男性男性单身
printf("\nSingle Males: ");
// 逐个条件过滤，与下面AndCriteria效果相同
FilterPersons *single_males = ((CriteriaMale *)criteria_male)->filter(filter_persons, criteria_male);
print_persons(((CriteriaSingle *)criteria_single)->filter(single_males, criteria_single));
printf("\nSingle Males: ");
// 通过AndCriteria来过滤
FilterPersons *single_males2 = ((AndCriteria *)single_male)->filter(filter_persons, single_male);
print_persons(single_males2);
// 查询女性或单身
printf("\nSingle Or Females: ");
print_persons(single_or_female->filter(filter_persons, (Criteria *)single_or_female));
free(filter_persons);
free(criteria_male);
free(criteria_female);
free(criteria_single);
free(single_male);
free(single_or_female);
return 0;
更多语言版本
不同语言实现设计模式：https://github.com/microwind/design-pattern
