链接器错误(link2005，link1169)

Question

当我试图编译时，我得到了这些错误：

我非常努力地解决所有的错误，但这三个赢了。我试了4个小时，因为我是个初学者。我非常感谢你们的帮助。

1)

错误1错误(??5cs52@@YAAAV?$basic_istream@DU?$char_traits@D@std@@@std@@AAV12@AAVSwimmingPool@0@@Z)："class std::basic_istream >& __cdecl cs52：：operator>>(类std::basic_istream > &，类in 52：：泳客&)“已在POOL.obj中定义

2)

错误2错误LNK2005："class std::basic_ostream >& __cdecl cs52::operator<<(class std::basic_ostream > &，class in 52：：泳池const &)“已在POOL.obj中定义

3)

错误3错误LNK1169:找到一个或多个被多重定义的符号

这是我的密码：

1)报头

#ifndef POOL_H
#define POOL_H
#include<iostream>


namespace cs52
{
    class SwimmingPool{



    public:
        SwimmingPool(int size);
        void fill(int amount);
        void splash();
        void swim();
        void evaporate(int amount);
        int getSize();
        int getContents();
        void setSize(int size);


    private:
        int mySize; // in gallons
        int myContents; // in gallons

        friend std::ostream& operator<<(std::ostream& outs, const SwimmingPool & pool);
        friend std::istream& operator>>(std::istream& ins, SwimmingPool & pool);
        friend SwimmingPool operator +(SwimmingPool& d, SwimmingPool& d2);
        friend SwimmingPool operator -(SwimmingPool& d, SwimmingPool& d2);

    };
    bool operator >(SwimmingPool& d, SwimmingPool& d2);
    bool operator <(SwimmingPool& d, SwimmingPool& d2);
    bool operator ==(SwimmingPool& d, SwimmingPool& d2);
    bool operator !=(SwimmingPool& d, SwimmingPool& d2);

    std::ostream& operator<<(std::ostream& outs, const SwimmingPool & pool){

        outs << "size " << pool.mySize << " contents " << pool.myContents;

        return outs;
    }
    std::istream& operator>> (std::istream& ins, SwimmingPool & pool)

    {
        std::cout << "enter size of pool\n";
        ins >> pool.mySize;
        pool.myContents = 0;
        return ins;
    }

}
#endif

2)这是我的第一个cpp文件

#include "POOL.h"
using namespace std;
using namespace cs52;
SwimmingPool::SwimmingPool(int size)
    {
        mySize = size;
        myContents = 0;
    }


void SwimmingPool::fill(int amount)
    {
        myContents += amount;

    }

    void SwimmingPool::splash()
    {
        cout << "splash" << std::endl;
    }


    void SwimmingPool::evaporate(int amount)
    {
        myContents -= amount;
    }


    int SwimmingPool::getSize()
    {
        return mySize;
    }


    int SwimmingPool::getContents()
    {
        return myContents;
    }

    void SwimmingPool::swim()
    {
        cout << "swimming\n";
    }
    bool cs52::operator >(SwimmingPool& d, SwimmingPool& d2)
    {
        if (d2.getSize() <d.getSize())
        {
            return true;
        }
        return false;
    }
    bool cs52::operator <(SwimmingPool& d, SwimmingPool& d2)
    {
        if (d2.getSize() >d.getSize())
        {
            return true;
        }
        return false;
    }
    bool cs52::operator ==(SwimmingPool& d, SwimmingPool& d2)
    {
        if (d2.getSize() == d.getSize())
        {
            return true;
        }

        return false;
    }
    bool cs52::operator !=(SwimmingPool& d, SwimmingPool& d2)
    {
        if (d2.getSize() != d.getSize())
        {
            return true;
        }

        return false;
    }

    SwimmingPool cs52::operator +(SwimmingPool& d, SwimmingPool& d2)
    {
        SwimmingPool s(d.getSize() + d2.getSize());
        s.fill(d.getContents() + d2.getContents());
        return s;
    }
    SwimmingPool cs52::operator -(SwimmingPool& d, SwimmingPool& d2)
    {
        if (d.getSize() >= d2.getSize() && d.getSize() >= d2.getSize())
        {
            SwimmingPool s(d.getSize() - d2.getSize());
            s.fill(d.getContents() - d2.getContents());
            return s;
        }
        else
            cout << "ERROR\n";
        return 0;
    }

3)这是我的主cpp文件

#include "POOL.h"
#include<iostream>

using namespace std;
using namespace cs52;
int main()
{
    SwimmingPool smallOne(1);
    SwimmingPool bigOne(1000);
    bigOne.fill(100);
    SwimmingPool yours(10);
    yours.fill(1);
    SwimmingPool mine(20);
    mine.fill(19);


    cout << "--some tests follow--" << endl;
    SwimmingPool pool1 = mine + mine;
    SwimmingPool pool2 = yours - yours;
    if (pool1 > pool2) {
        cout << "> is working..." << endl;
    }
    if (pool1 != pool2) {
        cout << "!= is working..." << endl;
    }
    if (pool2 < pool1) {
        cout << "< is working..." << endl;
    }
    if (pool1 == pool1) {
        cout << "== is working..." << endl;
    }
    cout << "---printing pool1---" << endl;
    cout << pool1 << endl;
    cout << "---printing pool2---" << endl;
    cout << pool2 << endl;
    cout << "---reading pool1---" << endl;
    cin >> pool1;
    cout << "---printing a revised pool1---" << endl;
    cout << pool1 << endl;
    cout << "---some broken code follows---" << endl;;
    SwimmingPool badPool = smallOne - bigOne;
    system("pause");
    return 0;
}

提前谢谢你，

Answer 1

在头文件中定义operator <<和operator >>空闲函数。这将导致将实现编译到两个对象文件中，从而导致定义重复。

你必须要么：

1. 将它们声明为inline
2. 将实现移动到CPP文件中。
3. 使重载的方法成为类的成员，并在类定义体中直接实现它们(实际上使它们成为inline)

选项1导致编译器不定义函数，而是将其实现复制到调用它的任何地方。当它是编译成DLL的API的一部分时，这可能会造成问题。在交换DLL时，函数中的更改不会影响现有程序，因为实现在主伪件中(二进制可重构性被破坏)。

在我看来，选项2是最好的选择，因为它将操作符实现绑定到类实现。

选项3在您的情况下不起作用，因为您的类必须是操作员的LHS (将在类的对象上调用操作符重载方法)。对于输入/提取操作符来说，情况并非如此。