【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

1. 可以通过层层筛选，过滤出自己想要的结果。
2. 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

1. 创建Criteria基础接口，定义过滤方法。
2. 创建多个条件类，实现过滤逻辑。
3. 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 filter(List 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;}@Overridepublic List filter(List persons) {List 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;}@Overridepublic List filter(List persons) {List firstCriteriaItems = criteria.filter(persons);List 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 {@Overridepublic List filter(List persons) {List femalePersons = new ArrayList();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 {@Overridepublic List filter(List persons) {List malePersons = new ArrayList();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 {@Overridepublic List filter(List persons) {List singlePersons = new ArrayList();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 persons = new ArrayList();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 
#include 
#include 
#include 
#include 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，敬请关注：GitHub - microwind/design-pattern: Design Pattern 经典设计模式 C/Java/Go/JavaScript/Python等不同语言详解 FP/OOP/MVC/MVP/MVVM/DDD等设计思想研究

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