错误4430当超载<<运算符

Question

我试图超载运算符为一个作业项目< <。我不断得到一个错误代码4430缺少类型说明符 - 假设为int。注意：C++不支持默认输入。任何帮助将是伟大的！

//EmployeeInfo is designed to hold employee ID information 

#ifndef EMPLOYEEINFO_H 
#define EMPLOYEEINFO_H 
#include <iostream> 
#include <ostream> 
using namespace std; 

std::ostream &operator << (std::ostream &, const EmployeeInfo &); 

class EmployeeInfo 
{ 
private: 
    int empID; 
    string empName; 

public: 
    //Constructor 
    EmployeeInfo(); 

    //Member Functions 
    void setName(string); 
    void setID(int); 
    void setEmp(int, string); 
    int getId(); 
    string getName(); 
    string getEmp(int &); 

    //operator overloading 
    bool operator < (const EmployeeInfo &); 
    bool operator > (const EmployeeInfo &); 
    bool operator == (const EmployeeInfo &); 

    friend std::ostream &operator << (std::ostream &, const EmployeeInfo &); 
}; 

friend std::ostream operator<<(std::ostream &strm, const EmployeeInfo &right) 
{ 
    strm << right.empID << "\t" << right.empName; 
    return strm; 
} 
#endif 

Answer 1

我觉得你的问题是与这条线：

std::ostream &operator << (std::ostream &, const EmployeeInfo &); 

此行EmployeeInfo类的声明之前出现。换句话说，编译器还不知道EmployeeInfo是什么。您也需要到申报转移到一个点类的声明，或“预申报”类像这样经过：

class EmployeeInfo; // "Pre-declare" this class 

std::ostream &operator << (std::ostream &, const EmployeeInfo &); 

class EmployeeInfo 
{ 
    // ... as you have now ... 
};