错误：重新定义班级 [英] error: redefinition of class

问题描述

这是我的代码：

// in main.cpp

#include "iostream"
#include "circle.cpp"
#include "rectangle.cpp"
#include "shape.cpp"

using namespace std;

int main() {
    Shape shapes[10];

    for (int i = 0; i < 10; i++){
        if (i % 2)
            shapes[i] = Circle(5);
        else
            shapes[i] = Rectangle(10, 10);

        cout << shapes[i].getArea();
    }

    return 0;
}


// in circle.cpp

#include "shape.cpp"

class Circle : public Shape {
    private:
        int radius;
        static const double PI = 3.14159265358979323846;

    public:
        Circle (int radius) : radius(radius) {}

        virtual int getArea() const {
            return PI * radius*radius;
        };

        virtual int setRadius(int radius){
            radius = radius;
        }
};


// in rectangle.cpp

#include "shape.cpp"

class Rectangle : public Shape {
    private:
        int width;
        int height;

    public:
        Rectangle(int width, int height) : width(width), height(height){}

        virtual int getArea() const {
            return width * height;
        }

        virtual void setWidth(int width){
            this->width = width;
        }

        virtual void setHeigth(int height){
            this->height = height;
        }
};


// in shape.cpp

class Shape {
    public:
        virtual int getArea() const = 0;
};

编译时出现此错误：

error: redefinition of 'class Shape'

如何我可以解决这个问题吗？

How can I fix this?

推荐答案

您应该在.h（标题）和.cpp文件（实现）之间构造代码。

You should structure your code between .h (headers) and .cpp files (implementation).

您应包含头文件： .h
切勿包含 .cpp 文件。 （除非您知道您要做什么，否则在极少数情况下会发生这种情况。）

You should include header files: .h Never include .cpp files. (Unless you know what you do, and that would be in really rare cases).

否则，您将结束几次类的编译，并且会收到编译器告诉您的错误：类的重新定义...

Otherwise you're ending compiling several times your class, and you get the error your compiler is telling you: 'redefinition of class...'

针对此错误的另一种保护措施是包括警卫队或标头警卫队。

An additional protection against this error are Include Guards, or Header Guards.

大多数编译器都支持类似 #pragma一次写在 .h 文件的顶部，以确保仅被编译一次。

Most compilers support something of the like #pragma once that you write at the top of .h files to ensure it is compiled only once.

如果编译器不适用于编译器，然后是传统的包含/标头保护系统：

If the pragma is not available for your compiler, then there is the traditionnal Include/Header guard system:

#ifndef MYHEADEFILE_H
#define MYHEADEFILE_H

// content of the header file

#endif

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