已经定义了运算符重载的错误

Question

调试我的程序时,我不断收到这两个错误:

main.obj:错误LNK2005:"class std :: basic_istream>&__cdecl operator >>(class std :: basic_istream>&,class Complex&)"(?? 5 @ YAAAV？$ basic_istream @ DU？$ char_traits @ D @ std @@@ std @@ AAV01 @ AAVComplex @@@ Z)已在Imaginary.obj中定义

1> main.obj:错误LNK2005:"class std :: basic_ostream>&__ cdecl operator <<(class std :: basic_ostream>&,class complex const&)"(?? 6 @ YAAAV？$ basic_ostream @ DU？$ char_traits @ D @ std @@@ std @@ AAV01 @ ABVComplex @@@ Z)已在Imaginary.obj中定义

我已经尝试重新启动我的项目,以确保我创建了一个控制台应用程序,而不是偶然的事情,但这不起作用.任何方向将不胜感激.

这是我的代码:

imaginary.h

#ifndef imaginary_h_
#define imaginary_h_

#include <iostream>

class Complex
{    
    friend std::ostream & operator << (std::ostream& os, const Complex&);
    friend std::istream & operator >> (std::istream& is, Complex&);

private:    
    double real;
    double imag;
    char op;

public:    
    double r = real;
    double i = imag;
    char o = op;

    Complex()
    {    
    }

    Complex(double r, double i, char o)
    {    
    }

    bool userTest();    
};

#endif

std::ostream & operator << (std::ostream & os, const Complex & complex)    
{
    os << complex.r << complex.o << complex.i << "i" << "/n" << "/n";
    return os;
}

std::istream & operator >> (std::istream & is, Complex & complex)    
{
    is >> complex.r >> complex.o >> complex.i;
    return is;
}

Imaginary.cpp

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

bool Complex::userTest()

{
    if (op == '+' || op == '-')

    {
        return true;
    }

    else

    {
        std::cout << "Incorrect operand entry, please enter complex number as x+yi" << "/n" << "/n";

                return false;
    }

}

main.cpp中

#include "imaginary.h"

#include <iostream>


int main()
{
    double userInput;

    std::cout << "Here you will add or subtract complex numbers." << "/n" << "/n";

    do

    {

        std::cout << "Please enter the real part of you complex number: " << "/n" << "/n";

                Complex complex;

        std::cin >> complex;

        std::cout << "/n" << "/n" << "/n/t" << "Note: Remember to enter your complex number in the format of x+yi to avoid an error";

                if (complex.userTest())
                {
                    std::cout << complex << "/n" << "/n";
                }

        std::cout << "Would you like to perform another complex number operation? " << "/n" << "/n/t";

                        std::cout << "Choose 1 for Yes and 2 for No" << "/n" << "/n";

        std::cin >> userInput;

    } while (userInput == 1);

    system("pause");

    return 0;
}

Answer 1

问题是你已经定义了

std::ostream & operator<<(std::ostream &os, const Complex &complex) {
    os << complex.r << complex.o << complex.i << "i" << "/n" << "/n";
    return os;
}

std::istream & operator>>(std::istream &is, Complex &complex) {
    is >> complex.r >> complex.o >> complex.i;
    return is;
}

在您的头文件中，因为它包含在其中imaginary.cpp并且main.cpp它们被多次定义。这违反了C++的单一定义规则。

你需要移动的实施operator <<，并operator >>在.cpp文件中，只留在头文件中的声明。这将意味着拥有

std::ostream & operator<<(std::ostream &os, const Complex &complex);

std::istream & operator>>(std::istream &is, Complex &complex);

在类定义之后的头文件中

class Complex {
    ...
};

而在结局之前#endif。然后在imaginary.cpp你会有定义

std::ostream & operator<<(std::ostream &os, const Complex &complex) {
    os << complex.r << complex.o << complex.i << "i" << "/n" << "/n";
    return os;
}

std::istream & operator>>(std::istream &is, Complex &complex) {
    is >> complex.r >> complex.o >> complex.i;
    return is;
}

Answer 2

您有两种选择:

1. 将operator方法的实现移动到单个cpp文件
2. 或者将实现声明为inline.

例如,在头文件imaginary.hpp中:

inline // <-- Add this line 
std::ostream & operator << (std::ostream & os, const Complex & complex)    
{
    os << complex.r << complex.o << complex.i << "i" << "/n" << "/n";
    return os;
}

inline  // <-- Add this line 
std::istream & operator >> (std::istream & is, Complex & complex)    
{
    is >> complex.r >> complex.o >> complex.i;
    return is;
}

#endif  // imaginary_h_  <-- This line was moved.

或者您可以简单地将实现移动到您的imaginary.cpp文件中.