C++ Class Inheritance: Functions

Question

I've been doing some coursework for the programming module of my Physics degree but I've been having some trouble. I had to make a class called Person and a subclass of that called Employee such that: Person.hpp:

#ifndef PERSON_HPP_
#define PERSON_HPP_

class Person {
public:
    Person(const std::string & name="Anonymous"): name(name) {;}
    ~Person() {;}

    std::string getname(){
        return name;
    }

    void setname(std::string newname) {
        name = newname;
    }

    void Print();

private:
    std::string name;
};

#endif /* PERSON_HPP_ */

Person.cpp:

void Person::Print(){
    std::string name = Person::getname;
    std::cout << name << std::endl;
}

Employee.hpp:

#ifndef EMPLOYEE_HPP_
#define EMPLOYEE_HPP_

class Employee: public Person {
public:
    Employee(const std::string & name, const std::string & job) : name(name), job(job){;}
    ~Employee() {;}

    std::string getjob(){
        return job;
    }

    void setjob(std::string newjob) {
        job = newjob;
    }

    void Print() const;

private:
    std::string job;
};

#endif /* EMPLOYEE_HPP_ */

Employee.cpp:

void Employee::Print(){
    Person::Print();
    std::string job = Employee::getjob;
    std::cout << job << std::endl;
}

main.cpp:

#include <iostream>
#include <string>
#include <vector>
#include "Person.hpp"
#include "Person.cpp"
#include "Employee.hpp"
#include "Employee.cpp"
#include "Friend.hpp"
#include "Friend.cpp"

int main() {
    return 0;
}

The error is in my employee.cpp. When building this error shows: ../Employee.cpp:10:6: error: use of undeclared identifier 'Employee'

I realise that I have probably made a very basic mistake however it is frustrating for me that I cannot see it.

Any help would be great! Thanks in advance, Sean Cooper

N.B. The purpose of employee.cpp is to print the name of the employee along with its associated job.

`#include "Employee.cpp"` -- here's where things started to go wrong. For sanity, you must separate interface from implementation (decl/defn). — Brian Cain, Mar 24 '14 at 18:00
Your cpp files should include the header files they need to include. Also, you don't want this -> `std::string job = Employee::getjob;`, you are declaring a local that hides the `job` member, just use `job` and it should work. — crashmstr, Mar 24 '14 at 18:02

score 1 · Answer 1 · answered Mar 24 '14 at 18:02

Your error is here:

#include "Employee.cpp"

Never include .cpp files, have them compiled as separate inputs for the linking stage.

Also don't forget to #include "Employee.hpp" in Employee.cpp file! Same things apply to #include "Person.cpp" etc. analogously.

iavr · Accepted Answer · 2014-03-24T18:08:42.697

Your include's should look like this:

Person.cpp:

#include <iostream>
#include <string>
#include "Person.hpp"

Employee.cpp:

#include <iostream>
#include <string>
#include "Employee.hpp"

main.cpp

#include <iostream>
#include <string>
#include <vector>
#include "Person.hpp"
#include "Employee.hpp"
#include "Friend.hpp"

That is, each .cpp (implementation) includes the respective .hpp (interface) along with additional headers needed (like <string>). Your main.cpp includes all needed headers but no other .cpp file. The compiler will parse all .cpp files individually and the linker will link the results into an executable. As a rule of thumb, never include a .cpp anywhere.

The specific error is when the compiler sees

void Employee::Print()

and doesn't know what Employee is. Including Employee.hpp fixes this by bringing in Employee's definition.

score 1 · Answer 3 · answered Mar 24 '14 at 18:02

You included several .cpp files, while I guess you intended to include header files.

Besides:

  Person::Print(); //this call is also wrong since Print() is not static
  std::string job = Employee::getjob;

getjob is a member function, you missed the () when you call the member function. Meanwhile, getjob() is not a static member function, it is supposed to be bounded with an object of the class. The way you are calling it is not correct. The same error occurs here:

 std::string name = Person::getname; //inside Print() function of Person

C++ Class Inheritance: Functions

3 Answers3