C++核心編程之類和對(duì)象詳解

更新時(shí)間：2021年09月03日 15:00:05 作者：Gigi Princess

這篇文章主要介紹了C++編程進(jìn)階之類和對(duì)象用法等相關(guān)使用技巧，需要的朋友可以參考下，希望能夠給你帶來幫助

1.封裝

1.1封裝的意義

將屬性和行為作為一個(gè)整體
將屬性和行為加以權(quán)限控制

封裝意義一：

語(yǔ)法：class 類名{ 訪問權(quán)限：屬性 / 行為 };

//實(shí)例1
#define _CRT_SECURE_NO_WARNINGS 1
//求圓的周長(zhǎng)
#include<iostream>
using namespace std;
#define pi 3.14
class circle
{
public:
	int m_d;//直徑
	double calculate()
	{
		return pi*m_d;
	}
};
int main()
{
	circle c1;
	c1.m_d = 10;
	cout << "圓周長(zhǎng)為" << c1.calculate() << endl;
	system("pause");
	return 0;
}

//實(shí)例2
#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
using namespace std;
#include <string>
class Student
{
public:
	string m_name;
	int m_num;
	void showStudent()
	{
		cout << " 姓名：" << "\t" << m_name << " 學(xué)號(hào)：" << m_num << endl;
	}
	void setname(string name)
	{
		m_name = name;
	}
	void setnum(int num)
	{
		m_num = num;
	}
};
int main()
{
	Student s1;
	s1.setname("zhangsan");
	s1.setnum(2001);
	s1.showStudent();
	Student s2;
	s2.setname("lisi");
	s2.setnum(2002);
	s2.showStudent();
    system("pause");
	return 0;
}

總結(jié)：類中的屬性和行為統(tǒng)一稱為成員

類中的屬性又稱為 成員屬性成員變量

類中的行為又稱為 成員函數(shù) 成員方法

封裝意義二

訪問權(quán)限有三種

公共權(quán)限： public 成員類內(nèi)可以訪問，類外可以訪問

保護(hù)權(quán)限： protected 成員類內(nèi)可以訪問，類外不可以訪問兒子可以訪問父親中的保護(hù)內(nèi)容

私有權(quán)限： private 成員類內(nèi)可以訪問，類外不可以訪問兒子不可以訪問父親中的保護(hù)內(nèi)容

#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
using namespace std;
#include <string>
class Student
{
public:
	string m_name;
protected:
	int m_num;
private:
	int m_age;
public:
	void func()
	{
		m_name = "lili";
		m_num = 1;
		m_age = 30;
	}
private:
	void func1()
	{
		m_name = "lili";
		m_num = 1;
		m_age = 30;
	}
};
int main()
{
	Student s1;
	s1.m_name = "lilllll";
	//s1.m_num = 2;//不可訪問
	//s1.m_age = 20;//不可訪問
	s1.func();
	//s1.func1();//不可訪問
    system("pause");
	return 0;
}

1.2 struct 和 class 區(qū)別

在C++中 struct 和 class 區(qū)別在于默認(rèn)的訪問權(quán)限不同

struct 默認(rèn)權(quán)限為公共
class 默認(rèn)權(quán)限為私有

#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
using namespace std;
class C1
{
	string m_a;
};
struct C2
{
	string m_b;
};
int main()
{
	//C1 c1;
	//c1.m_a = "lili";//不可訪問
	C2 c2;
	c2.m_b = "lili";
    system("pause");
	return 0;
}

1.3 成員屬性設(shè)置為私有

優(yōu)點(diǎn)：

將所有成員屬性設(shè)置為私有，可以自己控制讀寫權(quán)限
對(duì)于寫權(quán)限，我們可以檢測(cè)數(shù)據(jù)的有效性

#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
#include <string>
using namespace std;
class C1
{
public:
	void setname(string name)
	{
		m_name = name;
	}
	string getname()
	{
		return m_name;
	}
	int getnum()
	{
		return m_num;
	}
	void setage(int age)
	{
		m_age = age;
	}
private:
	string m_name;
	int m_num;
	int m_age;
};
int main()
{
	C1 c;
	c.setname("yangyang");//可寫
	cout << c.getname() << endl;//可讀
	cout << c.getnum() << endl;//只讀
	c.setage(30);//只寫
    system("pause");
	return 0;
}

好的，到這里封裝就算是學(xué)到手了，可以進(jìn)行兩個(gè)小案例：

#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
#include <string>
using namespace std;
class Cube
{
public:
	void setchang(int chang)
	{
		m_c = chang;
	}
	void setkuan(int kuan)
	{
		m_k = kuan;
	}
	void setgao(int gao)
	{
		m_g = gao;
	}
	int getchang()
	{
		return m_c;
	}
	int getkuan()
	{
		return m_k;
	}
	int getgao()
	{
		return m_g;
	}
	int S()
	{
		return 2 * (m_c*m_g + m_c*m_k + m_g*m_k);
	}
	int V()
	{
		return m_c*m_g*m_k;
	}
	bool isSamebyclass(Cube &c)
	{
		if (m_c == c.getchang() && m_g == c.getgao() && m_k == c.getkuan())
		{
			return true;
		}
		return false;
	}
private:
	int m_c;
	int m_k;
	int m_g;
};
bool isSame1(Cube &c1, Cube &c2)
{
	if (c1.getchang() == c2.getchang() && c1.getgao() == c2.getgao() && c1.getkuan() == c2.getkuan())
	{
		return true;
	}
	return false;
}
int main()
{
	Cube c1;
	c1.setchang(10);
	c1.setkuan(10);
	c1.setgao(10);
	cout << "面積：" << c1.S() << endl;
	cout << "體積：" << c1.V() << endl;
	Cube c2;
	c2.setchang(11);
	c2.setkuan(11);
	c2.setgao(11);
	cout << "面積：" << c2.S() << endl;
	cout << "體積：" << c2.V() << endl;
	bool ret = isSame1(c1, c2);
	if (ret)
	{
		cout << "全局函數(shù)判斷：兩個(gè)立方體相等" << endl;
	}
	else
	{
        cout << "全局函數(shù)判斷：兩個(gè)立方體不相等" << endl;
	}
	ret = c1.isSamebyclass(c2);
	if (ret)
	{
		cout << "成員函數(shù)判斷：兩個(gè)立方體相等" << endl;
	}
	else
	{
		cout << "成員函數(shù)判斷：兩個(gè)立方體不相等" << endl;
	}
	system("pause");
	return 0;
}

#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
#include <string>
using namespace std;
class Point
{
public:
	void setX(int x)
	{
		m_x = x;
	}
	int getX()
	{
		return m_x;
	}
	void setY(int y)
	{
		m_y = y;
	}
	int getY()
	{
		return m_y;
	}
private:
	int m_x;
	int m_y;
};
class Circle
{
public:
	void setR(int r)
	{
		m_r = r;
	}
	int getR()
	{
		return m_r;
	}
	void setcenter(Point center)
	{
		m_center = center;
	}
	Point getcenter()
	{
		return m_center;
	}
private:
	int m_r;
	Point m_center;
};
void C_and_P(Circle &c, Point &p)
{
	int distance = (c.getcenter().getX() - p.getX())*(c.getcenter().getX() - p.getX()) + (c.getcenter().getY() - p.getY())* (c.getcenter().getY() - p.getY());
	int doubleR = c.getR()*c.getR();
	if (distance==doubleR)
	{
		cout << "點(diǎn)在圓上" << endl;
	}
	else if (distance<doubleR)
	{
		cout << "點(diǎn)在圓內(nèi)" << endl;
	}
	else
	{
		cout << "點(diǎn)在圓外" << endl;
	}
}
int main()
{
	Point p;
	p.setX(10);
	p.setY(30);
	Circle c;
	c.setR(10);
	Point center;
	center.setX(26);
	center.setY(43);
	C_and_P(c, p);
    system("pause");
	return 0;
}