C++ istream运算符重载 - 不能访问数据成员，即使声明的朋友

Question

我有一个类复杂，我想重载istream运算符>>，以允许用户输入一个复杂的数字形式“（a，b ）”。以下是我的头文件和我的实现。现在，我收到一个错误，说我的重载的>>函数不能访问真实或想象的数据成员，因为它们是不可访问的，即使我在类头文件中将它们声明为朋友。任何人都可以解释我没有看到什么吗？

头文件

// 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 

实现文件：

// 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

你的错误是在这里

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

这不符合您定义的（正确的）签名

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