Heap memory and Stack memory

  • Different ways to initialize pointers

    • int * a = # create a pointer points to num on stack memory
    • Cube * cube = new Cube; create a pointer points to cube on heap memory

  • When deleting a pointer, we need to assign the pointer to nullptr even if the the memory will be released after the function is returned

  • Pointer can use -> to obtain the class attribute, otherwise we need dereference and use dot (cube->attribute <=> (*cube).attribute)

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    int *x = new int;
int &y = *x;  //y is the alias of heap memory stored *x

Constructors

  • Default constructor/ Customized constructor

  • Copy constructor (copy constructors are invoked automatically)

    • Passing an object as a parameter (by value)

    • Returning an object from a function (by value)

    • Initializing a new object

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      Cube::Cube(const Cube & obj)
{
length_ = obj.length_;
std::cout << "Copy constructor invoked!" << std::endl;
}

int main()
{
Cube c;
Cube b;
Cube myCube = c; // copy constructor will be called
b = c            //copy constructor will not be called
return 0;
}

  • Assign constructor

    • Is a public member function of the class.

    • Has the function name operator=

    • Has a return value of a reference of the class’ type.

    • Has exactly one argument

      • The argument must be const reference of the class’ type.

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        Cube & Cube::operator= (const Cube & obj)
{
length_ = obj. length;
std::cout << "Assignment operator invoked!"<< std::endl;
return *this;
}

  • Destructor (~). An destructor should neverbe called directly. Instead, it is automatically called when the object’s memory is being reclaimed by the system:

    • If the object is on the stack, when the function returns
    • If the object is on the heap, when delete is used