求圆的周长和面积的多文件实现
一个类对应一个头文件和一个.cpp文件，在头文件写类的声明，在.cpp文件中写类的实现。
1 //Circle.h
2 #pragma once
3
4 class Circle
5 {
6 public:
7 //设置半径
8 void set(double r);
9 //得到半径
10 double get();
11 //得到周长
12 double getCircleGirth();
13 //得到面积
14 double getCircleArea();
15 private:
16 double m_r;
17 double m_area;
18 double m_girth;
19
20 };
1 //Circle.cpp
2
3 #include "Circle.h"
4
5 void Circle::set(double r)
6 {
7 m_r = r;
8 }
9
10 //得到半径
11 double Circle::get()
12 {
13 return m_r;
14 }
15 //得到周长
16 double Circle::getCircleGirth()
17 {
18 m_girth = 2 * 3.14*m_r;
19 return m_girth;
20 }
21 //得到面积
22 double Circle::getCircleArea()
23 {
24 m_area = 3.14*m_r*m_r;
25 return m_area;
26 }
//主文件
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include "Circle.h"
using namespace std;
int main(void)
{
Circle c;
c.set(10);
cout << "圆的半径：" << c.get() << endl;
cout << "圆的周长：" << c.getCircleGirth() << endl;
cout << "圆的面积：" << c.getCircleArea() << endl;
}
