a simple payroll system using linked list c++ - c++

Question

i am simply creating a payroll system that has a employee name and a working hours for that employee.. the data is supposed to be stored in a linked list data structure, but i can not connect the linked list to the object of the class employee, i tried making the pay roll linked list (i.e empList) as a static member so that all the objects of the class can use the same list object and data can be stored but once i compile my code i get an error of "undefined reference to employee::empList" at line 130 that is the last line of constructor, same error on line 150 that is a print pay roll function.. where ever i am trying to call any payRollLinkedList class's function in employee class it gives error.. bottom line is that all i want is to data be stored in a doubly linked list of employees and i can not access the list.
#include <iostream>
using namespace std;
class payRollLinkedList;
class node
{
private:
node* previousPointer;
string name;
int hoursWorked;
node* nextPointer;
friend class payRollLinkedList;
public:
explicit node(const string argName, const int argHoursWorked)
: previousPointer{nullptr}, name{argName}, hoursWorked{argHoursWorked}, nextPointer{nullptr}
{}
};
class payRollLinkedList
{
private:
node* headPointer{nullptr};
node* tailPointer{nullptr};
node* getNewNode(const string argName, const int argHoursWorked)
{
return new node(argName, argHoursWorked);
}
public:
void addAtBack(const string argName, const int argHoursWorked)
{
node* newNode{getNewNode(argName, argHoursWorked)};
if(isEmpty())
{
headPointer = tailPointer = *newNode;
}
else
{
tailPointer->nextPointer = newNode;
newNode->previousPointer = tailPointer;
tailPointer = newNode;
newNode = nullptr;
delete newNode;
}
}
bool deleteNode(string argName)
{
node* currentPointer{headPointer};
if(isEmpty())
{
cout <<"the list is already empty\n";
return false;
}
else
{
while(currentPointer != nullptr)
{
if(currentPointer->name == argName)
{
if(currentPointer == headPointer)
{
node* tempPointer{headPointer};
headPointer = headPointer->nextPointer;
tempPointer->nextPointer = nullptr;
headPointer->previousPointer = nullptr;
delete tempPointer;
break;
}
if(currentPointer == tailPointer)
{
node*tempPointer{tailPointer};
tailPointer = tailPointer->previousPointer;
tempPointer->previousPointer = nullptr;
tailPointer->nextPointer = nullptr;
delete tempPointer;
break;
}
node* tempPointer{currentPointer};
node* nextPtr{tempPointer->nextPointer};
currentPointer = currentPointer->previousPointer;
currentPointer->nextPointer = nextPtr;
nextPtr->previousPointer = currentPointer;
tempPointer->nextPointer = nullptr;
tempPointer->previousPointer = nullptr;
currentPointer = nullptr;
nextPtr = nullptr;
delete tempPointer;
delete currentPointer;
delete nextPtr;
}
else
currentPointer = currentPointer->nextPointer;
}
return true;
}
}
void print()
{
if(isEmpty())
{
cout <<"nothing to show\n";
return;
}
else
{
node* currentPointer{headPointer};
while(currentPointer != nullptr)
{
cout <<currentPointer->name <<"\t";
currentPointer = currentPointer->nextPointer;
}
}
}
bool isEmpty()
{
return headPointer == nullptr? true : false;
}
};
class employee
{
private:
string name;
int hoursWorked;
static payRollLinkedList empList;
public:
employee()
: name{""}, hoursWorked{0}
{}
employee(string argName, int argHoursWorked)
{
name = argName;
hoursWorked = argHoursWorked;
empList.addAtBack(name, hoursWorked);
}
void printPayRoll()
{
empList.print();
}
};
int main()
{
employee emp("usman", 12);
employee emp1("ali", 12);
emp.printPayRoll();
}

Answer 1

https://en.cppreference.com/w/cpp/language/static
You need to define static member of class at global scope (out of class).
i suggest you to split your code .h and .cpp files and define the member in .cpp file.
payRollLinkedList employee::empList;