错误LNK 2019未解析的外部符号类std :: basic_istream

Question

我正在尝试重载输出和输入流操作符，但在编译时会出现此错误

  

错误1错误LNK2019：未解析的外部符号“类   std :: basic_istream＆gt; ＆安培; __cdecl   运算符＆gt;＆gt;（类std :: basic_istream

     

    

＆amp;，class complex const＆amp;）“（?? 5 @ YAAAV？$ basic_istream @ DU？$ char_traits @ D @ std @@@ std @@ AAV01 @ ABVComplex @@@ Z）     在函数中引用     _main C：\ Users \ owner \ Documents \ Personal \ practice \ main.obj practice

  

基本上我试图读取用户输入并将其解析为实数和虚数

Complex.h

#pragma once
#include <iostream>
using namespace std;

class Complex
{
public:
    Complex(void);
    ~Complex(void);
    friend ostream& operator<<(ostream&, const Complex &C);
    friend istream& operator>>(istream&, const Complex &C);
    int real;
    int imaginary;
};

Complex.cpp

#include "Complex.h"

using namespace std;

Complex::Complex()
{
    real = 0;
    imaginary = 0;
}


Complex::~Complex(void)
{
}

ostream &operator<<(ostream &output, const Complex &C)
{
    char symbol = '+';
    if (C.imaginary < 0)
        symbol = '-';
    output << C.real << ' ' << symbol << ' ' << abs(C.imaginary) << 'i';
    return output;
}

istream &operator>>(istream &input, Complex &C)
{
    int tempReal;
    char symbol;
    char tempImaginaryFull[2];
    int tempImaginary;
    input >> tempReal >> symbol >> tempImaginaryFull;
    C.real = tempReal;
    tempImaginary = tempImaginaryFull[0];
    C.imaginary = tempImaginary;
    if( symbol == '-')
        C.imaginary *= -1;

    return input;
}

我真的不知道那个错误意味着什么，即使我已经尝试过寻找它。