c++项目导入头文件声明及定义

代码如下：

---

Shape.h

#ifndef SHAPE_H_INCLUDED
#define SHAPE_H_INCLUDED

class Shape{

public:
    virtual float GetPircumference()=0;


};

class Rectangle:public Shape
{

private:
    float R_a;
    float R_b;
public:
    Rectangle(float a,float b);
    float GetPircumference();

};

class Circle:public Shape
{

private:
    float C_a;
public:
    Circle(float a);
    float GetPircumference();

};

#endif // SHAPE_H_INCLUDED

---

Shape.cpp

#include<iostream>

#include "Shape.h"

//Rectangle::Rectangle(int a,int b):Rectangle::R_a(a),R_b(b){}//这种初始化一般用在没有分头文件声明和具体实现，this用的多
Rectangle::Rectangle(float a,float b)
{
    this->R_a =a;
    this->R_b =b;
}

float Rectangle::GetPircumference()
{
    float R_c =0;
    R_c = 2*(this->R_a + this->R_b;
    return R_c;
}

//Circle::Circle(int a):Circle::C_a(a){}
Circle::Circle(float a)
{
    this->C_a =a;
}

float Circle::GetPircumference()
{
    float R_c =0;
    R_c = 2*this->C_a*3.14;
    return R_c;
}

---

main.cpp

#include <iostream>

#include "Shape.h"

using namespace std;

int main()
{
    Shape *rect =new Rectangle(3,4);
    cout <<rect->GetPircumference()<<endl;
    Shape *cirle =new Circle(5);
    cout <<cirle->GetPircumference()<<endl;
    return 0;
}

---

编译出错：

解决办法：

• 右键点击项目
  
• 然后把未勾选的都选上并点击OK
  
  
• 最后重新编译运行

问题原因：

• 新建file时候（.h或者.cpp）未勾选编译类型
  
  
  
• 参考：https://blog.youkuaiyun.com/lonely_gfwolf/article/details/77837650