30天学习C++从入门到入土 --- Day03

骑猪看日落 2023-06-14 10:47 11阅读 0赞

### 文章目录 ###

*  类和对象
 *   *  基本概念
     *   *  类的封装
         *   *  1. 把属性和方法进行封装
             *  2. 对属性和方法进行控制
             *  3.没有访问控制限定的成员变量 函数 默认是私有属性
             *  4. 类的内部和类的外部
             *  5. class 和 struct关键字的区别
             *  6. 类的声明和类的实现分开
     *  案例
     *   *  1
         *  2
         *  3

# 类和对象 #

## 基本概念 ##

1.  类、对象、成员变量、成员函数
2.  类的基本特性:  
    封装、继承、多态

### 类的封装 ###

#### 1. 把属性和方法进行封装 ####

#### 2. 对属性和方法进行控制 ####

private
    public 
    protected

#### 3.没有访问控制限定的成员变量 函数 默认是私有属性 ####

#### 4. 类的内部和类的外部 ####

public修饰成员变量和成员函数可以在类的内部和类的外部被访问
     private修饰成员变量和成员函数只能在类的内部被访问

#include<iostream>
    using namespace std;
    
    class myCircle
    { 
    public:
    	double getR()
    	{ 
    		return m_r;
    	}
    	void setR(double r)
    	{ 
    		m_r = r;
    		//return m_r;
    	}
    
    	double getS()
    	{ 
    		m_s = 3.14 * m_r * m_r;
    		return m_s;
    	}
    private:
    	double m_r;
    	double m_s;
    
    };
    //类和指针
    //类做函数参数
    //类封装了成员函数和成员变量
    void printMyCircle01(myCircle* mpc)
    { 
    	cout << "r:" << mpc->getR()<< endl;
    	cout << "s:" << mpc->getS()<< endl;
    }
    
    //类和引用
    void printMyCircle02(myCircle& mpc)
    { 
    	cout << "r:" << mpc.getR() << endl;
    	cout << "s:" << mpc.getS() << endl;
    }
    
    int main()
    { 
    	myCircle c1, c2;
    	//c1.m_r = 10;//私有成员外部不能直接访问
    	c1.setR(10);
    	cout << c1.getS() << endl;
    	cout << endl;
    	c1.setR(20);
    	printMyCircle01(&c1);
    	cout << endl;
    	c1.setR(20);
    	printMyCircle02(c1);
    
    	return 0;
    }

![在这里插入图片描述][20191119145937942.png]  
![在这里插入图片描述][20191119141508799.png]

#### 5. class 和 struct关键字的区别 ####

> 在用struct定义类时，所有成员的默认属性为public  
> 在用class定义类时，所有成员的默认属性为private

#### 6. 类的声明和类的实现分开 ####

**类的声明  
MyTeacher.h**

#pragma once//只包含一次 防止重定义
    
    //类的声明
    class MyTeacher
    { 
    public:
    	void setAge(int age);
    	int getAge();
    private:
    	int m_age;
    };

**类的实现  
MyTeacher.cpp**

#include "MyTeacher.h"
    
    //类的实现
    //类域作用符 也相当于写在了类的内部
    void MyTeacher::setAge(int age)
    { 
    	m_age = age;
    }
    
    int MyTeacher::getAge()
    { 
    	return m_age;
    }

MyMain.cpp

#include<iostream>
    #include "MyTeacher.h"
    
    using namespace std;
    
    int main()
    { 
    	MyTeacher t;
    	t.setAge(30);
    	cout << t.getAge() << endl;
    
    	return 0;
    }

## 案例 ##

### 1 ###

> 设计立方体类(cube)，求出立方体的面积和体积  
> 求两个立方体，是否相等（全局函数和成员函数）

#include<iostream>
    using namespace std;
    
    //设计立方体类(cube)，求出立方体的面积和体积
    //比较立方体是否一样
    class Cube 
    { 
    private:
    	int m_a;
    	int m_b;
    	int m_c;
    	int m_v;
    	int m_s;
    public:
    	void setABC(int a, int b, int c)
    	{ 
    		m_a = a;
    		m_b = b;
    		m_c = c;
    	}
    
    	int getA()
    	{ 
    		return m_a ;
    	}
    	int getB()
    	{ 
    		return m_b ;
    	}
    	int getC()
    	{ 
    		return m_c ;
    	}
    
    	int getS()
    	{ 
    		m_s = 2 * (m_a * m_b + m_a * m_c + m_b * m_c); 
    		return m_s;
    	}
    	int getV()
    	{ 
    		m_v = m_a * m_b * m_c;
    		return m_v;
    	}
    	//②
    	//问题抛出 冗余
    	int judge(Cube& c1, Cube& c2)
    	{ 
    		if ((c1.getA() == c2.getA()) &&
    			(c1.getB() == c2.getB()) &&
    			(c1.getC() == c2.getC()))
    		{ 
    			return 1;
    		}
    		else
    		{ 
    			return 0;
    		}
    	}
    	//③
    	int judge(Cube& c2)
    	{ 
    		//这里的m_a是调用它的对象的成员变量
    		if( (m_a == c2.getA())&&
    			(m_b == c2.getB())&&
    			(m_c == c2.getC()))
    		{ 
    			return 1;
    		}
    		else
    		{ 
    			return 0;
    		}
    	}
    
    };
    //①全局函数
    //1:same ; 0 : not same
    int judge(Cube& c1, Cube& c2)
    { 
    	if ((c1.getA() == c2.getA())&&
    		(c1.getB() == c2.getB())&&
    		(c1.getC() == c2.getC()))
    	{ 
    		return 1;
    	}
    	else
    	{ 
    		return 0;
    	}
    }
    
    int main()
    { 
    	Cube c1, c2;
    	c1.setABC(1, 2, 3);
    	c2.setABC(1, 2, 4);
    	cout << c1.getS() << endl;
    	cout << c1.getV() << endl;
    
    	//②
    	//冗余
    	if (c1.judge(c1, c2) == 1)
    	{ 
    		cout << "same" << endl;
    	}
    	else
    	{ 
    		cout << "not same" << endl;
    	}
    
    	//③
    	if (c1.judge(c2) == 1)//通过c1对象的类 调用成员函数
    	{ 
    		cout << "same" << endl;
    	}
    	else
    	{ 
    		cout << "not same" << endl;
    	}
    
    	//①
    	if (judge(c1,c2) == 1)
    	{ 
    		cout << "调用全局变量 same" << endl;
    	}
    	else
    	{ 
    		cout << "调用全局变量 not same" << endl;
    	}
    	return 0;
    }

### 2 ###

> 设计一个圆形类（Circle），和一个点类（Point），计算点在圆内部还是圆外  
> 即：求点和圆的关系（圆内和圆外）

#include<iostream>
    using namespace std;
    
    class Point
    { 
    private:
    	int p_x;
    	int p_y;
    public:
    	void setPoint(int x, int y)
    	{ 
    		p_x = x;
    		p_y = y;
    	}
    	int getp_X()
    	{ 
    		return p_x;
    	}
    	int getp_Y()
    	{ 
    		return p_y;
    	}
    };
    
    class Circle
    { 
    private:
    	int c_r;
    	int c_x;
    	int c_y;
    public:
    	void setCircle(int r, int x, int y)
    	{ 
    		c_x = x;
    		c_y = y;
    		c_r = r;
    	}
    	int getR()
    	{ 
    		return c_r;
    	}
    	int getc_X()
    	{ 
    		return c_x;
    	}
    	int getc_Y()
    	{ 
    		return c_y;
    	}
    
    	int judge(Point& p)
    	{ 
    		//计算两点之间的距离
    		double a = abs((c_x - p.getp_X()) * (c_x - p.getp_X()) + (c_y - p.getp_Y()) * (c_y - p.getp_Y()));
    		
    		//1：点在圆内 0：点在圆外
    		if (c_r >= a)
    		{ 
    			return 1;
    		}
    		else
    		{ 
    			return 0;
    		}
    	}
    };
    
    
    int main()
    { 
    	Circle c;
    	c.setCircle(10, 12,10);
    
    	Point p;
    	p.setPoint(10, 100);
    
    	//1 面向对象
    	if ((c.judge(p)) == 1)
    	{ 
    		cout << "点在圆内" << endl;
    	}
    	else
    	{ 
    		cout << "点在圆外" << endl;
    	}
    
    	//2 
    	double a = abs((c.getc_X() - p.getp_X()) * (c.getc_X() - p.getp_X()) + (c.getc_Y() - p.getp_Y()) * (c.getc_Y() - p.getp_Y()));
    
    	if(c.getR() > a)
    	{ 
    		cout <<"点在圆内" << endl;
    	}
    	else
    	{ 
    		cout <<"点在圆外"  << endl;
    	}
    
    	return 0;
    
    }

### 3 ###

> 把2中类的声明和实现分开

**Circle.h**

#pragma once
    #include "Point.h"
    
    class Circle
    { 
    private:
    	int c_r;
    	int c_x;
    	int c_y;
    public:
    	void setCircle(int r, int x, int y);
    	int getR();
    	int getc_X();
    	int getc_Y();
    
    	int judge(Point& p);
    
    };

**Circle.cpp**

#include "Circle.h"
    #include "Point.h"
    #include<iostream>
    
    void Circle::setCircle(int r, int x, int y)
    { 
    	c_x = x;
    	c_y = y;
    	c_r = r;
    }
    int Circle::getR()
    { 
    	return c_r;
    }
    int Circle::getc_X()
    { 
    	return c_x;
    }
    int Circle::getc_Y()
    { 
    	return c_y;
    }
    
    int Circle::judge(Point& p)
    { 
    	//计算两点之间的距离
    	double a = abs((c_x - p.getp_X()) * (c_x - p.getp_X()) + (c_y - p.getp_Y()) * (c_y - p.getp_Y()));
    
    	//1：点在圆内 0：点在圆外
    	if (c_r >= a)
    	{ 
    		return 1;
    	}
    	else
    	{ 
    		return 0;
    	}
    }

**Point.h**

#pragma once
    
    class Point
    { 
    private:
    	int p_x;
    	int p_y;
    public:
    	void setPoint(int x, int y);
    	int getp_X();
    	int getp_Y();
    };

**Point.cpp**

#include "Point.h"
    
    void Point::setPoint(int x, int y)
    { 
    	p_x = x;
    	p_y = y;
    }
    int Point::getp_X()
    { 
    	return p_x;
    }
    int Point::getp_Y()
    { 
    	return p_y;
    }

**main.cpp**

#include<iostream>
    #include "Circle.h"
    #include "Point.h"
    using namespace std;
    
    int main()
    { 
    	Circle c;
    	c.setCircle(10, 12, 10);
    
    	Point p;
    	p.setPoint(10, 100);
    
    	//1
    	if ((c.judge(p)) == 1)
    	{ 
    		cout << "点在圆内" << endl;
    	}
    	else
    	{ 
    		cout << "点在圆外" << endl;
    	}
    
    	return 0;
    
    }

[20191119145937942.png]: https://img-blog.csdnimg.cn/20191119145937942.png
[20191119141508799.png]: https://img-blog.csdnimg.cn/20191119141508799.png