[英]C++ Virtual Void
好吧,所以我有一个称为雇员的父类和一个称为经理,研究人员和工程师的3个子类。 我做了一个向量,想列出它们。 这就是我制作过程的方式。
vector <Employee*,Manager*> EmployeeDB;
Employee *temp;
temp = new Manager(first, last, salary, meetings, vacations);
EmployeeDB.push_back(temp);
我制作矢量没有问题,我的担心是列出信息。 这3个子类都具有firstname
, lastname
和salary
但它们的区别在于它们具有不同的数据成员,这是唯一的,例如Manager
具有int
值vacation
,而Engineer
具有int
值experience
等等。
Employee.h :
#include <iostream>
#include <string>
using namespace std;
#ifndef EMPLOYEE_h
#define EMPLOYEE_h
class Employee
{
public:
Employee();
Employee(string firstname, string lastname, int salary);
string getFname();
string getLname();
int getSalary();
virtual void getInfo();
private:
string mFirstName;
string mLastName;
int mSalary;
};
#endif
Employee.cpp :
#include "Employee.h"
#include <iostream>
#include <string>
using namespace std;
Employee::Employee()
{
mFirstName = "";
mLastName = "";
mSalary = 0;
}
Employee::Employee(string firstname, string lastname, int salary)
{
mFirstName = firstname;
mLastName = lastname;
mSalary = salary;
}
string Employee::getFname()
{
return mFirstName;
}
string Employee::getLname()
{
return mLastName;
}
int Employee::getSalary()
{
return mSalary;
}
void Employee::getInfo()
{
cout << "Employee First Name: " << mFirstName << endl;
cout << "Employee Last Name: " << mLastName << endl;
cout << "Employee Salary: " << mSalary << endl;
}
主要 :
#include <vector>
#include <iostream>
#include <string>
#include "Employee.h"
#include "Engineer.h"
#include "Manager.h"
#include "Researcher.h"
using namespace std;
vector <Employee*> EmployeeDB;
Employee *temp;
void add()
{
int emp, salary, vacations, meetings, exp, c;
string first, last, type, school, topic;
bool skills;
do
{
system("cls");
cout << "===========================================" << endl;
cout << " Add Employee " << endl;
cout << "===========================================" << endl;
cout << "[1] Manager." << endl;
cout << "[2] Engineer." << endl;
cout << "[3] Researcher." << endl;
cout << "Input choice: ";
cin >> emp;
system("cls");
} while (emp <= 0 || emp > 3);
cout << "===========================================" << endl;
cout << " Employee Info " << endl;
cout << "===========================================" << endl;
cout << "Employee First name: ";
cin >> first;
cout << "Employee Last name: ";
cin >> last;
cout << "Employee Salary: ";
cin >> salary;
switch (emp)
{
case 1:
cout << "Employee numbers of meetings: ";
cin >> meetings;
cout << "Employee numbers of vacations: ";
cin >> vacations;
temp = new Manager(first, last, salary, meetings,vacations);
EmployeeDB.push_back(temp);
delete temp;
break;
case 2:
cout << endl;
cout << "[1]YES [2]NO" << endl;
cout << "Employee C++ Skills: ";
cin >> c;
if (c == 1)
{
skills = true;
}
else
{
skills = false;
}
cout << "Employee Years of exp: ";
cin >> exp;
cout << "(e.g., Mechanical, Electric, Software.)" << endl;
cout << "Employee Engineer type: ";
cin >> type;
temp = new Engineer(first, last, salary, skills, exp, type);
EmployeeDB.push_back(temp);
delete temp;
break;
case 3:
cout << "Employee School where he/she got his/her PhD: ";
cin >> school;
cout << "Employee Thesis Topic: ";
cin >> topic;
temp = new Researcher(first, last, salary, school, topic);
EmployeeDB.push_back(temp);
delete temp;
break;
}
}
void del()
{
}
void view()
{
for (int x = 0; x < (EmployeeDB.size()); x++)
{
cout << EmployeeDB[x]->getInfo();
}
}
void startup()
{
cout << "===========================================" << endl;
cout << " Employee Database " << endl;
cout << "===========================================" << endl;
cout << "[1] Add Employee." << endl;
cout << "[2] Delete Employee." << endl;
cout << "[3] List Employees." << endl;
cout << "[4] Exit." << endl;
cout << "Please Enter Your Choice: ";
}
int main(int argc, char** argv)
{
bool flag = true;
int choice;
do {
do
{
system("cls");
system("pause>nul");
startup();
cin >> choice;
} while (choice < 0 || choice >4);
switch (choice)
{
case 1:
add();
break;
case 2:
del();
break;
case 3:
view();
break;
case 4:
flag = false;
system("EXIT");
break;
}
} while (flag == true);
return 0;
system("pause>nul");
}
我在view()
函数上遇到错误。
它说没有operator<<
与这些操作数二进制'<<'匹配:没有找到采用void等右手操作数的运算符。
问题在于getInfo
返回类型为void
并且您试图将返回值放入cout中。
重要的是要了解代码std::cout << val
实际上调用函数operator<<(ostream& out, const objectType& val)
,其中objectType是'val'的类型。
在您的情况下,该类型为void,并且根本没有实现将void作为类型的operator<<
实现。 因此,出现错误“找不到运算符,该运算符采用void类型的右手操作数”。
为了解决您的问题,您有几种选择:
将view()
更改为
for (...) { EmployeeDB[x]->getInfo(); }
更改getInfo()
以根据需要返回字符串信息:
std::string getInfo() { std::string info; info =... return info; }
为Employee创建一个operator<<
并更改视图以调用它:
view() { for (...) { std::cout << EmployeeDB[x]; } }
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