朋友不允许在课堂定义之外

Question

我正试图在任务中删除cout操作符，我被迫并要求将我的类拆分为（.h和.cpp）。这是我的完整代码：

instructor.h

#include "person.h"
#ifndef instructor_h
#define instructor_h
class instructor: public person {

private:    
    int children;
    int salary;
    string maritalStatus;

public:

    instructor();
    instructor(string, string, string, int , int ,string);

instructor operator++();

    void print();



    int calcSalary();

    int getSalary();
    int getNumOfChildren();
    string getMarialStatus();

    friend ostream &operator <<(ostream, instructor );
    void setSalary(int);
    void getNumOfChildren(int);
    void setMarialStatus(string);

};

#endif

instructor.cpp

#include <iostream>
#include <string>
#include "instructor.h"
using namespace std;

instructor::instructor() {

}


instructor::instructor(string a , string b, string c , int chil , int sal ,string mar):person(a,b,c) 

{
    children = chil;
    salary = sal;
    maritalStatus = mar;
}


instructor instructor::operator ++()
    {
        children=children+1;
        return *this;
    }


int instructor::calcSalary() {

    int new_sal;
    new_sal = salary + children*0.1;

    return new_sal;
}

int instructor::getSalary() {

    cout <<"Here is the result of your query:"<<endl;
    cout <<"================================="<<endl;
    cout<< "Salary: "<<salary<<""<<endl;
    cout <<"================================="<<endl;
    cout <<endl;

    return salary;


}

int instructor::getNumOfChildren() {

    cout <<"Here is the result of your query:"<<endl;
    cout <<"================================="<<endl;
    cout<< "Number of children: "<<children<<""<<endl;
    cout <<"================================="<<endl;


    cout <<endl;
    return children;


}

string instructor::getMarialStatus() {

    cout <<"Here is the result of your query:"<<endl;
    cout <<"================================="<<endl;
    cout<< "Marital Status: "<<maritalStatus<<""<<endl;
    cout <<"================================="<<endl;
    cout <<endl;

    return maritalStatus;

}


friend ostream& operator<<(ostream& os, instructor& v){
    os << v.children;

return os;
}



void instructor::setSalary(int sal) {

    salary = sal;
}

void instructor::getNumOfChildren(int nmc) {

    children = nmc;

}

void instructor::setMarialStatus(string sms) {

    maritalStatus = sms;

}



void instructor::print() {

    person::print();
    cout <<"Here is the result of your query:"<<endl;
    cout <<"================================="<<endl;
    cout<< "Marital Status: "<<maritalStatus<<""<<endl;
    cout<< "Number of children: "<<children<<""<<endl;
    cout<< "Salary: "<<salary<<""<<endl;
    cout <<"================================="<<endl;
    cout <<endl;


}

我收到以下错误：

  

instructor.cpp（75）：错误C2255：'friend'：不允许在类定义之外    instructor.cpp（76）：错误C2248：'instructor :: children'：不能   访问类'讲师'中声明的私有成员1＆gt;
  c：\ documents and settings \ george \ my documents \ visual studio   2005 \ projects \ hana \ hana \ instructor.h（7）：见声明   '讲师::孩子'1＆gt;
  ==========构建：0成功，1个失败，0个最新，0个跳过==========

我正在使用visual studio 2005.为什么我会收到这些错误？

所有这一切都是由于我尝试重载运算符cout：

friend ostream& operator<<(ostream& os, instructor& v){
    os << v.children;

return os;
}

为什么不工作？

Answer 1

有两个问题。第一个是你不能在课堂外使用friend，正如错误所说的那样。但你不需要;已经将该功能宣布为班级中的朋友，您只需将其定义在外面，而无需再次提及朋友。

但另一个问题是您的声明和定义不匹配。你宣布这是朋友：

ostream &operator <<(ostream, instructor );

然后你定义了这个：

ostream& operator<<(ostream&, instructor&)

那些不一样，但它们必须是。