C++ istream運算符重載 - 不能訪問數據成員，即使聲明的朋友

Question

我有一個類複雜，我想重載istream運算符>>，以允許用戶輸入一個複雜的數字形式「（a，b ）」。以下是我的頭文件和我的實現。現在，我收到一個錯誤，說我的重載的>>函數不能訪問真實或想象的數據成員，因爲它們是不可訪問的，即使我在類頭文件中將它們聲明爲朋友。任何人都可以解釋我沒有看到什麼嗎？

頭文件

// Complex class definition. 
#ifndef COMPLEX_H 
#define COMPLEX_H 

class Complex 
{ 
friend std::ostream &operator<<(std::ostream &, const Complex &); 
friend std::istream &operator>>(std::istream &, const Complex &); 
public: 
    explicit Complex(double = 0.0, double = 0.0); // constructor 
    Complex operator+(const Complex &) const; // addition 
    Complex operator-(const Complex &) const; // subtraction 
    //Complex operator*(const Complex &); // function not implemented yet 
private: 
    double real; // real part 
    double imaginary; // imaginary part 
}; // end class Complex 

#endif 

實現文件：

// Complex class member-function definitions. 
#include <iostream> 
#include <iomanip> 
#include "Complex.h" // Complex class definition 
using namespace std; 

// Constructor 
Complex::Complex(double realPart, double imaginaryPart) 
    : real(realPart), 
    imaginary(imaginaryPart) 
{ 
    // empty body 
} // end Complex constructor 

// addition operator 
Complex Complex::operator+(const Complex &operand2) const 
{ 
    return Complex(real + operand2.real, 
     imaginary + operand2.imaginary); 
} // end function operator+ 

// subtraction operator 
Complex Complex::operator-(const Complex &operand2) const 
{ 
    return Complex(real - operand2.real, 
     imaginary - operand2.imaginary); 
} // end function operator- 

// display a Complex object in the form: (a, b) 
ostream &operator<<(ostream &out, const Complex &operand2) 
{ 
    out << "(" << operand2.real << ", " << operand2.imaginary << ")"; 

    return out; // enable cascading output 
} 

// change the imaginary and real parts 
istream &operator>>(istream &in, Complex &operand2) 
{ 
    in.ignore(); // skips '(' 
    in >> setw(1) >> operand2.real; // get real part of the number 
    in.ignore(2); //ignore the , and space 
    in >> setw(1) >> operand2.imaginary; 
    in.ignore(); // skip ')' 
    return in; // enable cascading input 
} 

Answer 1

你的錯誤是在這裏

friend std::istream &operator>>(std::istream &, const Complex &); 
               // ^^^^^ 

這不符合您定義的（正確的）簽名

istream &operator>>(istream &in, Complex &operand2)