C++ Copy Constructor & Operator Overloading

Question

I am relatively new to classes and was introduced to copy constructors and overloading last week. I am supposed to overload the = operator and use it to assign multiple variables using the class name.

For some reason, running the program causes a popup saying

program.cpp has stopped responding.

I am positive there are minor/major things that I am missing due to me being a rookie with objects in C++.

Any advice is very much appreciated!

#include<iostream>
#include<string>

using namespace std;

class Employee
{
private:
    char *name;
    string ID;
    double salary;
public:
    Employee() {}
    Employee(char *name, string eid, double salary) {}

    Employee(const Employee &obj)
    {
        name = new char;
        ID = obj.ID;
        salary = obj.salary;
    }

    ~Employee() {}

    void setName(char *n)
    {
        name = n;

    }

    void setID(string i)
    {
        ID = i;
    }

    void setSalary(double s)
    {
        salary = s;
    }

    char getName()
    {
        return *name;
    }

    string getID()
    {
        return ID;
    }

    double getSalary()
    {
        return salary;
    }

    Employee operator = (Employee &right)
    {
        delete[] name;
        ID = right.ID;
        salary = right.salary;
        return *this;
    }

};

int main()
{
    Employee e1("John", "e222", 60000), e2(e1), e3, e4;

    e3 = e4 = e2;

    e2.setName("Michael");
    e2.setSalary(75000);
    e3.setName("Aaron");
    e3.setSalary(63000);
    e4.setName("Peter");


    cout << "\nName: " << e1.getName() << "\nID: " << e1.getID() <<     "\nSalary: " << e1.getSalary() << endl;
    cout << "\nName: " << e2.getName() << "\nID: " << e2.getID() <<     "\nSalary: " << e2.getSalary() << endl;
    cout << "\nName: " << e3.getName() << "\nID: " << e3.getID() <<     "\nSalary: " << e3.getSalary() << endl;
    cout << "\nName: " << e4.getName() << "\nID: " << e4.getID() <<     "\nSalary: " << e4.getSalary() << endl;

    return 0;
}

Answer 1

There are several issues with this code.

The first issue is in the constructor Employee(char *name, string eid, double salary) {} which is just doing nothing and ignoring the passed data whereas it should be using it to initialize the fields (class member data).

Employee(char *name, string eid, double salary) 
{
    const size_t bufferSize = strlen(name) + 1; 
    this->name = new char[bufferSize];
    memcpy(this->name, name, bufferSize);

    this->ID = eid;
    this->salary = salary; 
}

The second issue is in the copy constructor Employee(const Employee &obj) , where you are just initializing the name (with single byte of char) and that's it. What the copy constructor suppose to do is initialize the fields (class members) of the class with the fields of the class object being passed to it.

Employee(const Employee &obj)
{
    const size_t bufferSize = strlen(name) + 1; 
    this->name = new char[bufferSize];
    memcpy(this->name, name, bufferSize);
    ID = obj.ID;
    salary = obj.salary;
}

the third issue is with the default constructor which is suppose to initialize the name pointer with the NULL so that the destructor could clean it up nicely:

Employee() : name(NULL) {}

~Employee() 
{
    if (NULL != name)
        delete[] name;
}

the fourth and last problem is with the assignment operator that's suppose to properly initialize the name member data instead of deleting it (which doesn't make sense)

Employee operator = (Employee &right)
{
    if (NULL != this->name)
        delete[] this->name;

    const size_t bufferSize = strlen(right.name) + 1; 
    this->name = new char[bufferSize];
    memcpy(this->name, right.name, bufferSize);
    ID = right.ID;
    salary = right.salary;
    return *this;
}

Answer 2

The problem is this line:

        delete[] name;

You shouldn't delete anything you haven't allocated with new first. If you delete the above line, your program kind of works. :)

Answer 3

Here's a slightly revised version of your program that works:

#include<iostream>
#include<string>

using namespace std;

class Employee
{
private:
    char *name;
    string ID;
    double salary;
public:
    Employee() {}
    Employee(char *name, string eid, double salary)
        : name (name) // ADDED THESE
        , ID(eid)
        , salary(salary)
    {

    }

    Employee(const Employee &obj)
    {
        name = obj.name; // WAS: new char;
        ID = obj.ID;
        salary = obj.salary;
    }

    ~Employee() {}

    void setName(char *n)
    {
        name = n;
    }

    void setID(string i)
    {
        ID = i;
    }

    void setSalary(double s)
    {
        salary = s;
    }

    char * getName()
    {
        return name;
    }

    string getID()
    {
        return ID;
    }

    double getSalary()
    {
        return salary;
    }

    Employee operator = (const Employee &right)
    {
        name = right.name; // WAS: delete[] name;
        ID = right.ID;
        salary = right.salary;
        return *this;
    }

};

int main()
{
    Employee e1("John", "e222", 60000), e2(e1), e3, e4;

    e3 = e4 = e2;

    e2.setName("Michael");
    e2.setSalary(75000);
    e3.setName("Aaron");
    e3.setSalary(63000);
    e4.setName("Peter");


    cout << "\nName: " << e1.getName() << "\nID: " << e1.getID() << "\nSalary: " << e1.getSalary() << endl;
    cout << "\nName: " << e2.getName() << "\nID: " << e2.getID() << "\nSalary: " << e2.getSalary() << endl;
    cout << "\nName: " << e3.getName() << "\nID: " << e3.getID() << "\nSalary: " << e3.getSalary() << endl;
    cout << "\nName: " << e4.getName() << "\nID: " << e4.getID() << "\nSalary: " << e4.getSalary() << endl;

    return 0;
}