What's wrong with this? Setters/Getters (edited ) header files included - c++

Question

when I have the following member in a class
employee headOfDepartment;
what's wrong these setters and getters?
void department::setHeadOfDepartment( employee depEmployee)
{
headOfDepartment=depEmployee;
}
employee department::getHeadOfDepartment()
{
return headOfDepartment;
}
I've been trying forever to define setters & getters with composition and it keeps getting me this error: "field ‘headOfDepartment’ has incomplete type"
ok Those are the header files:
#ifndef EMPLOYEE_H_
#define EMPLOYEE_H_
using namespace std;
#include <iostream>
#include <vector>
#include "department.h"
#include "project.h"
class department;
class project;
//#include <vector>
employee.h
class employee
{
string Name; //text with spaces
string National_ID; //unique value (text) for each employee
static double Salary; // value of 1500 pounds
char Gender; //character holds f or m
int Available_vacations; //initially starts with 15 days
static double Deduction_per_day; // value of 85.5 pounds
int Available_permission_hours; //initially starts with 20 hours
static double Deduction_per_hour; // value of 15.5 pounds
double Actual_salary; // value with actual salary after deductions
int Vacations; // vacations employee took
int Permessions; // permession hours employee took
int empSerialNum; // object order in vector
department* myDepartment;
vector < project > empProjects;
public:
employee (); // default constructor
employee (string myName, string myNationalID, char myGender,int mySerialNum); // Parameterized constructor
~employee(); // Destractor
//Setters
void setName(string myName);
void setNationalID (string myNationalID);
void setGender (char myGander);
void setAvailableVacation(int myAvVac);
void setAvailablepermissionhours (int myAvPerHours);
void setActualSalary (double actualSalary);
void setVacations(int myVacations);
void setPermessions(int myPermessions);
void setempSerialNum(int mySerialNum);
void setDepartment(department*);
void addProject(project);
//Getters
string getName();
string getNationalID ();
char getGender ();
int getAvailableVacation();
int getAvailablepermissionhours ();
double getActualSalary ();
int getVacations ();
int getPermessions ();
int getempSerialNum();
department* getDepartment();
project* getProjects();
void view (); // View to view Name, ID and actual salary
void View_Detailed (); //call previous function and also shows other details (vacations - permissions - detailed deductions - ... )
void Free_All(); //return all values to default
double Take_vacation(); //this function takes number of days employee need to take as vacation, available vacations reduced by number of days given, if available vacations became 0 salary is deduced by deduction per day set
double Take_permession(); //this function takes hours that employee asked to take, reduce available permission hour by hours given, if available permission become 0 hour salary is reduced by deduction per ho
double Calculate_Actual_Salary();// calculates salary after deductions and returns it
};
#endif
department.h
#ifndef DEPARTMENT_H_
#define DEPARTMENT_H_
using namespace std;
#include <string.h>
#include "employee.h"
#include "project.h"
#include <vector>
class project;
class employee;
class department{
private:
string name;
string ID;
employee headOfDepartment;
vector <project> depprojects; //projects managed by the department
public:
//constructors
department();
department(string, string);
//Setters
void setName(string);
void setID(string);
void setHeadOfDepartment( employee /*const&*/ depEmployee);
void addProject(project);
//Getters
string getName();
string getID();
employee getHeadOfDepartment() /*const*/;
// project getProjects();
};
#endif
project.h
#ifndef PROJECT_H_
#define PROJECT_H_
#include <string.h>
#include "department.h"
#include "project.h"
class department;
class project{
string name;
department* location;
public:
//constructors
project();
project(string proName, department* proDepartment);
//Setters
void setName(string proName);
void setLocation(department* proDepartment);
//Getters
string getName();
department* getLocation();
};
#endif

Answer 1

You need to the include the header file where employee is declared in your header and source files for department

Answer 2

Class employee shall be defined before using it as a type name of an object. Also I advice to add qualifier const for the getter

Answer 3

You are not including the header that defines employee in your department class header, but you have a non-reference non-pointer declaration of type employee in your header.