Question

This is correct code from a classmate the professor bragged about and I cant understand why it requires a double constructor i originally only had the first function and couldnt figure out it required two which lagged my progress as a professional

class Studentrecords
{
private:

    struct student
    {
        string name;
        string address;
        int ID;
        double gpa;
    };

    student *stackArray;
    int stackSize;
    int top;

public:
    Studentrecords();
    Studentrecords(int size);
    ~Studentrecords();
    void push(string name, string address, int id, double gpa);
    void pop();
    bool isFull() const;
    bool isEmpty() const;
    void display();
};

Studentrecords::Studentrecords(int size)
{
    stackArray = new student[size];
    top = 0;
}

Studentrecords::Studentrecords()
{
    stackSize = 25;
    stackArray = new student[stackSize];
    top = 0;
}

Studentrecords::~Studentrecords()
{
    delete [] stackArray;
}

Answer 1

It doesn’t require two constructors, that’s just how the class is defined. That way, you can create an object in two ways:

Studentrecords s(15);

which will create a Studentrecords object of size 15, or

Studentrecords s;

which will call the default constructor, and create an object of type Studentrecords and size 25.

I must note that this is bad code though:

• The default Studentrecords() constructor can be replaced with Studentrecords(int size = 25) to avoid code duplication.
• no use of initializer lists
• you’re managing memory in the class, which means you’d need a copy constructor and copy assignment operator
• finally, you’re using a C-style array instead of a std::vector.