Objects & Class

	What is an object?
		component of a program
		contains variables and data
		perform certain actions
		interact with other pieces of the program
	What is a class?
		blue prints of objects
		abstraction data type (ADT)

Instance

	Instance – every object is an instance of a class
		a real thing of a class
		can be manipulated
		instances keep track of their own information
		called member data/variables
		knows how to do things with different methods

Method

	Method (interface)
		member variable except it can do more tricks
		like move(), attackMonster() and etc..
		Special methods
			Constructors
				get the object ready to be used
			Destructors
				terminate the object

Struct and Class

	struct Player{
	int health;
	int strength;
	int agility;
	}
	Player Jane, John;
	class Player {
	public:
	int health;
	int strength;
	int agility;
	};
	Player Jane, John;

Constructors & Destructors

	Player:: Player () {
		strength = 10;
		agility = 10;
		health = 10;
		}
	Player::~Player() {
	strength = 0;
	agility = 0;
	health = 0;
	} //automatically called

Instantiation

	Purpose
		set up an object: i.e. instantiate an object.
	How
		Constructor automatically invoked at declaration time
			Player John;   //default constructor
		Player::Player(int s, int a) {
			strength = stg;
			agility = agl;
			health = 10;
			}
			Player Jane(20, 5); //function overloading

"class Player {"

	class Player {
	int health;
	int strength;
	int agility;
	Player();              // constructor - no return type
	Player(int s, int a);  // alternate constructor void  void move();
	void attackMonster();
	void getTreasure();
	};

"class Player {"

	class Player {
	private: // hidden
	int health;
	int strength;
	int agility;
	public:
	Player();              // constructor - no return type
	Player(int s, int a);  // alternate constructor void  void move();
	void attackMonster();
	void getTreasure();
	};

"void Player::move()..."

	void Player::move() {
	cout <<“I’ve moved to a new position.” << endl;
	}
	void Player::getTreasure() {
	health++;  // increments health by one
	}
	int main() {
	Player Jane, John(5, 5);
	cout <<“Jane’s  health:.” << Jane.health << endl;
	Jane.getTreasure();
	cout <<“Jane’s  health:.” << Jane.health << endl;
	};

"class Engine {"

	class Engine {
	public:
	void start() const {}
	void rev() const {}
	void stop() const {}
	};
	class Wheel {
	public:
	void inflate(int psi) const {}
	};

"class Window {"

	class Window {
	public:
	void rollup() const {}
	void rolldown() const {}
	};
	class Door {
	public:
	Window window;
	void open() const {}
	void close() const {}
	};

"class Car {"

	class Car {
	public:
	Engine engine;
	Wheel wheel[4];
	Door left, right; // 2-door
	};
	int main() {
	Car car;
	car.left.window.rollup();
	car.wheel[0].inflate(72);
	}