SOLID 设计原则

单一职责原则（SRP）

单一职责原则是指每个类设计的时候职责尽可能单一，因此只有该职责需要变化时才需要修改这个类。尽可能少的修改代码。

开闭原则

开闭原则就是对扩展开放，对修改关闭。已经写好的类，当需要修改或者增加新的扩展功能时，不需要修改已经写好测试过的代码。

里氏替换原则

某个接口以基类对象做为参数，那么它因该同等地接受子类对象做为参数，并且程序不会产生任何异常。

接口隔离原则

接口隔离原则地基本思想是将复杂的接口分离为多个单独的接口，以避免强制实现者必须实现某些他们实际上并不需要的接口。

依赖倒转原则

高层模块不应该依赖低层模块，他们都应该依赖抽象接口。抽象接口不应该依赖细节，细节应该依赖抽象接口。
为为

创建型模式

构造器模式

传统构造方法

构造器模式主要是用于复杂对象的构造，复杂对象的内部具有多个成员变量，构造的时候往往采用具有多个形参的构造函数，多个形参具有多种组合，导致构造函数要写多个；或者在构造后调用set函数给成员变量赋值。

#include "pch.h"
#include <iostream>
#include <string>using namespace std;class Student
{
public:Student();Student(int id){this->id = id;}Student(int id, int score, const string & name){this->id = id;this->score = score;this->name = name;}Student(int id, int age){this->id = id;this->age = age;}void setId(int id){this->id = id;}void setScore(int score){this->score = score;}void setName(const string & name){this->name = name;}void setAdress(const string & adress){this->adress = adress;}~Student();private:int id;int score;string name;string adress;int age;
};Student::Student()
{
}Student::~Student()
{
}int main()
{Student student1(0, 100, "xiaoming");Student student2;student2.setName("xiaoli");student2.setId(1);student2.setScore(99);student2.setAdress("lock street");std::cout << "Hello World!\\n"; 
}

使用上述方法构造对象的时候显得很麻烦，要么需要写多个类型的构造函数，要么需要多次调用set。使用构造器就可以使得构造变得更加灵活简洁。

构造器

jave实现

Java典型的Builder模式需要的类

• 需要构造的实体类
• 实体类中需要一个具体的构造类
• 构造类中需要聚合一个需要构造的实体类对象
• 构造类中需要写各种构造该实体类中不同属性的方法
• 构造类中还需要一个构造结束的方法build()，返回的对象是内聚的实体类

/* 典型的java中builder模式* @Author ChenJiahao(程序员五条)* @Date 2021/9/22 22:43*/
public class Person {int id;String name;int age;double weight;int score;Location loc;private Person(){}public static class PersonBuilder{Person p = new Person();public PersonBuilder basicInfo(int id,String name,int age){p.id = id;p.name = name;p.age = age;return this;}public PersonBuilder weight(double weight){p.weight = weight;return this;}public PersonBuilder score(int score){p.score = score;return this;}public PersonBuilder loc(String street,String roomNo){p.loc = new Location(street,roomNo);return this;}public Person build(){return p;}}@Overridepublic String toString() {return "Person{" +"id=" + id +", name='" + name + '\\'' +", age=" + age +", weight=" + weight +", score=" + score +", loc=" + loc +'}';}
}/* Person中引用的属性* @Author ChenJiahao(程序员五条)* @Date 2021/9/22 22:39*/
public class Location {String street;String roomNo;public Location(String street, String roomNo) {this.street = street;this.roomNo = roomNo;}
}/* @Author ChenJiahao(程序员五条)* @Date 2021/9/22 22:55*/
public class Test {public static void main(String[] args) {// 下面.后面的不想要的可以注掉Person p = new Person.PersonBuilder().basicInfo(1,"zhangsan",18)// .score(20).weight(200)// .loc("bj","23").build();System.out.println(p);}
}

C++语言实现

#include "pch.h"
#include <iostream>
#include <string>using namespace std;class StudentBuilder;class Student
{friend class StudentBuilder;
public:static unique_ptr<StudentBuilder> build(){return make_unique<StudentBuilder>();}void PrintInfo(){cout << "id:" << id << endl << "score:" << score << endl << "name:" << name << endl << "adress:"<< adress << endl << "age:" << age << endl;}~Student() {};private:int id;int score;string name;string adress;int age;Student() {};
};class StudentBuilder
{
public:StudentBuilder() {};~StudentBuilder() {};StudentBuilder& id(int id){student.id = id;return *this;}StudentBuilder& score(int score){student.score = score;return *this;}StudentBuilder& name(const string & name){student.name = name;return *this;}StudentBuilder& adress(const string & adress){student.adress = adress;return *this;}operator Student() const { return student; }
private:Student student;
};int main()
{Student student1 = Student::build()->adress("block Street").id(1).name("xiaoming").score(100);student1.PrintInfo();std::cout << "Hello World!\\n"; 
}

C++语言 实现的构造器有个问题，就是构造的时候会执行一遍复制构造函数，导致效率低。得益于java语言的内存管理机制，java语言实现简便。C++语言的构造器还需要再继续优化。