作者:billy
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过滤器模式
过滤器模式(Filter Pattern),又叫标准模式(Criteria Pattern),是一种结构型模式,通过结合多个标准来获得单一标准。
这种设计模式允许开发人员使用不同的标准来过滤一组对象,通过逻辑运算以解耦的方式把它们连接起来。
使用场景
当你在一个很庞大的数据量中查找一些东西时,可以使用过滤器模式制定过滤规则,然后根据指定的标准进行过滤,得到符合条件的数据。
优缺点
-
优点:
1、体现了各功能模块的“黑盘”特性及高内聚、低耦合的特点。
2、可以将整个系统的输入,输出行为看成是多个过滤器行为的简单合成。
3、支持软件功能模块的重用。
4、便于系统维护:新的过滤器可以添加到现有系统中来,旧的可以由改进的过滤器替换。
5、支持某些特定的分析,如吞吐量计算、死锁检测等。
6、支持并行操作,每个过滤器可以作为一个单独的任务完成。 -
缺点:
1、通常导致系统处理过程的成批操作。
2、需要设计者协调两个相对独立但又存在关系的数据流。
3、可能需要每个过滤器自己完成数据解析和合成工作(如加密和解密),从而导致系统性能下降,并增加了过滤器具体实现的复杂性。
注意事项
1、构建过滤规则时不要太繁琐。
2、注意区分过滤和拦截的功能差异。
UML结构图
代码实现
person.h
构建类 Person,可输出自己的属性,判断是否在一个数组中
#include <string>
#include <vector>
#include <iostream>
using namespace std;
class Person
{
public:
Person(string name, string gender, int age) : name(name), gender(gender), age(age) {}
void printf()
{
cout << "student name: " + name +
", gender: " + gender +
", age: " + std::to_string(age) << endl;
}
bool judVec(std::vector<Person*> vec)
{
auto iter = std::find(std::begin(vec), std::end(vec), this);
return (iter == std::end(vec));
}
string getName() { return this->name; }
string getGender() { return this->gender; }
int getAge() { return this->age; }
private:
string name;
string gender;
int age;
};
interface.h
创建抽象类 - 过滤器;创建实体类 - 过滤器、男性过滤器、女性过滤器、年龄过滤器
男性和年龄过滤器、女性或年龄过滤器
#include "person.h"
#include <algorithm>
class Criteria //基类-过滤器
{
public:
Criteria() {}
virtual ~Criteria() {}
virtual std::vector<Person *> filter(std::vector<Person *> vector) = 0;
};
class MaleCriteria: public Criteria //子类-男性过滤器
{
public:
std::vector<Person *> filter(std::vector<Person *> vector)
{
std::vector<Person *> result;
for(size_t i = 0; i < vector.size(); i++)
{
if(vector.at(i)->getGender() == "male")
{
result.push_back(vector.at(i));
}
}
return result;
}
};
class FemaleCriteria: public Criteria //子类-女性过滤器
{
public:
std::vector<Person *> filter(std::vector<Person *> vector)
{
std::vector<Person *> result;
for(size_t i = 0; i < vector.size(); i++)
{
if(vector.at(i)->getGender() == "female")
{
result.push_back(vector.at(i));
}
}
return result;
}
};
class AgeCriteria: public Criteria //子类-年龄过滤器
{
public:
std::vector<Person *> filter(std::vector<Person *> vector)
{
std::vector<Person *> result;
for(size_t i = 0; i < vector.size(); i++)
{
if(vector.at(i)->getAge() > 18) {
result.push_back(vector.at(i));
}
}
return result;
}
};
class AndCriteria: public Criteria //子类-与 && 过滤器
{
public:
AndCriteria(Criteria *firstCriteria, Criteria *secondCriteria): firstCriteria(firstCriteria), secondCriteria(secondCriteria) {}
std::vector<Person *> filter(std::vector<Person *> vector)
{
std::vector<Person *> firstvector = firstCriteria->filter(vector);
return secondCriteria->filter(firstvector);
}
private:
Criteria *firstCriteria;
Criteria *secondCriteria;
};
class OrCriteria: public Criteria //子类- 或 || 过滤器
{
public:
OrCriteria(Criteria *firstCriteria, Criteria *secondCriteria) : firstCriteria(firstCriteria), secondCriteria(secondCriteria) {}
std::vector<Person *> filter(std::vector<Person *> vector)
{
std::vector<Person *> firstvector = firstCriteria->filter(vector);
std::vector<Person *> secondvector = secondCriteria->filter(vector);
for(auto it: firstvector)
{
if (it->judVec(secondvector))
{
secondvector.push_back(it);
}
}
return secondvector;
}
private:
Criteria *firstCriteria;
Criteria *secondCriteria;
};
main.cpp
实例应用 - 根据不同的过滤规则获取不同的数据
#include "interface.h"
int main()
{
std::vector<Person *> vector;
Person *stu1 = new Person("Billy", "male", 25);
Person *stu2 = new Person("Kitty", "female", 24);
Person *stu3 = new Person("Alice", "female", 23);
Person *stu4 = new Person("Ben", "male", 17);
Person *stu5 = new Person("Jeason", "male", 18);
Person *stu6 = new Person("Jon", "male", 20);
Person *stu7 = new Person("Miss", "female", 13);
Person *stu8 = new Person("Abbey", "female", 14);
vector.push_back(stu1);
vector.push_back(stu2);
vector.push_back(stu3);
vector.push_back(stu4);
vector.push_back(stu5);
vector.push_back(stu6);
vector.push_back(stu7);
vector.push_back(stu8);
Criteria *maleCriteria = new MaleCriteria();
Criteria *femaleCriteria = new FemaleCriteria();
Criteria *ageCriteria = new AgeCriteria();
Criteria *andCriteria = new AndCriteria(maleCriteria, ageCriteria);
Criteria *orCriteria = new OrCriteria(femaleCriteria, ageCriteria);
std::vector<Person *> malevector = maleCriteria->filter(vector);
std::vector<Person *> femalevector = femaleCriteria->filter(vector);
std::vector<Person *> agevector = ageCriteria->filter(vector);
std::vector<Person *> andvector = andCriteria->filter(vector);
std::vector<Person *> orvector = orCriteria->filter(vector);
cout << "male:" << endl;
for(auto it: malevector)
{
it->printf();
}
cout << endl << "female:" << endl;
for(auto it: femalevector)
{
it->printf();
}
cout << endl << "age > 18:" << endl;
for(auto it: agevector)
{
it->printf();
}
cout << endl << "male and age > 18:" << endl;
for(auto it: andvector)
{
it->printf();
}
cout << endl << "female or age > 18:" << endl;
for(auto it: orvector)
{
it->printf();
}
return 0;
}
运行结果:
male:
student name: Billy, gender: male, age: 25
student name: Ben, gender: male, age: 17
student name: Jeason, gender: male, age: 18
student name: Jon, gender: male, age: 20
female:
student name: Kitty, gender: female, age: 24
student name: Alice, gender: female, age: 23
student name: Miss, gender: female, age: 13
student name: Abbey, gender: female, age: 14
age > 18:
student name: Billy, gender: male, age: 25
student name: Kitty, gender: female, age: 24
student name: Alice, gender: female, age: 23
student name: Jon, gender: male, age: 20
male and age > 18:
student name: Billy, gender: male, age: 25
student name: Jon, gender: male, age: 20
female or age > 18:
student name: Billy, gender: male, age: 25
student name: Kitty, gender: female, age: 24
student name: Alice, gender: female, age: 23
student name: Jon, gender: male, age: 20
student name: Miss, gender: female, age: 13
student name: Abbey, gender: female, age: 14