overloading_overriding_const_constructors_enums.md

Overloading & overriding

Overloading - when you have multiple functions with the same name

void Donate(Book b);
void Donate(Book b, int copies);

overriding - providing a new version of some function with a specific signature

bool operator==(const Book & other);
Book operator+(const Book & other);

const

keyword - means "unchangeable"

• parameters - function can't modify the param's value

• variables - value can't change

• pointers - location that it's pointing to can't be changed

• methods - method can't modfy the object on which it is called

• use const type & as input parameters in general

• use const methods for getters and other methods that shouldn't change the object instance

const int x = 7;

Constructors

• in c++, all classes have a default, 0-param constructor provided UNTIL you write any constructor yourself
• if we initialize an array of some class:

Point p_arr[3];  // Point's 0-param constructor * 3

• initialization lists:

Point::Point(const int x, const int y):
    x_(x),
    y_(y),
    z_(0) {
    // regular body of constructor, will be run 2nd, after initialization list
}

Initialization lists are faster, so we prefer to use them when possible.

enums (enumerations)

• set of related named constants
• creating your own (mini) custom type
• define a Color type
• define a Month type

enum class Name{value1, value2, ... , valueN};
enum class Day{Monday, Tuesday, Wednesday, ... };

why class? it prevents c++ from being overeager at converting enums to ints

Name var = Name::value1;
Day today = Day::Tuesday;

if (var == Name::value2) {

}