Question

I am studying for my midterm exam. There is going to be a question about setting up an array dynamically, and maybe doing a copy constructor, a destructor and overloading the assignment operator. Can you please verify if I am correct. Also I don’t understand what overloading the assignment operator means. Can you help me out with this?

class A { int* myArray;   //basically I created a pointer called myArray,  A()             //are my copy constructors correct? A(), and A(int size)? {     myArray = 0; } A(int size) {     myArray = new int[size]; } ~A()             // I think my destructor is correct {     delete [] myArray; } 

Can you check my code please? Also how do I overload assignment operator?

Thanks in advance.

Answer 1

The copy constructor is used for creation of object based on another’s instance of the same type. You don’t have such. You can define it using code like this:

A(const A &other) {    myArray = new int[other._size];    _size = other._size;    memcpy(myArray, other.myArray, sizeof(int) * _size); } 

You should change your class, so it will store _size of array, you also need to change visibility of your constructors and destructor to public.

The overloaded assignment operator should look like this:

const A &operator=(const A &other) {    if(this == &other) return *this; // handling of self assignment, thanks for your advice, arul.    delete[] myArray; // freeing previously used memory    myArray = new int[other._size];    _size = other._size;    memcpy(myArray, other.myArray, sizeof(int) * _size);    return *this; } 

You also can add a check of equality of array sizes in this assignment operator, so you will reuse your dynamic array without unnecessary reallocations of memory.