1. Andy Wang Object Oriented Programming in C++ COP 3330
Arrays and Classes
Andy Wang
Object Oriented Programming in C++
COP 3330

2. Arrays of Objects Declaring
Array is an indexed collection of data elements of the same type
Index is between 0 and size – 1
We can have array of objects
Fraction rationals[20]; // array of 20 Fraction objects
Complex nums[50]; // an array of 50 Complex objects
Hydrant fireplugs[10]; // an array of 10 objects of type Hydrant
In an array of objects, each array position is a single object
rationals has 20 objects named rationals[0], rationals[1]…rationals[19]

3. Initialization Normally, the constructor initializes an object
The default constructor (if available) is invoked for each object in an array
Fraction numList[4]; // builds 4 fractions using default constructor

4. Initialization
With different constructors, which constructor is invoked for each object in an array?
Use initializer set
Fraction numList[3] = { Fraction(2,4), Fraction(5), Fraction() };
// allocates an array of 3 fractions, initialized to 2/4, 5/1, and 0/1.

5. Using Arrays of Objects
Indexing the same as with regular arrays
Dot-operator works the same as with single names
objectName.memberName
Name of each object is arrayName[index]
Examples
Fraction rationals[20]; // create an array of 20 Fraction objects
rationals[2].Show(); // displays the third Fraction object
rationals[6].Input(); // calls Input function for the 7th Fraction
cout << rationals[18].Evaluate();

6. Arrays as Class Member Data
C-style arrays are pretty primitive
No boundary checks; unsafe
Array can be used as a member data of a class
Member functions can error check boundary conditions
A good way to create safer array types

7. Example: DList
dlist/
List of up to 10 values of type double, not always full
Member data current tracks the number of elements in the list
The list is not the same as the array
The array is the physical storage used by the class
The list is an abstract concept that an object of this class type represents

8. Example: DList Note since the array is member data of a class
No need to pass the array as a parameter

9. dlist.h
const int MAX = 10; class DList { public: DList(); bool Insert(double item); // inserts item (if room) double GetElement(unsigned int index) const; void Print() const; // prints the list int GetSize() const; // number of stored items private: double array[MAX]; int current; // number of stored items };

10. dlist.cpp
#include <iostream> #include “DList.h” using namespace std; DList::DList() { current = 0; } bool DList::Insert(double item) { if (current >= MAX) return false; array[current] = item; current++; return true; }

11. dlist.cpp
double DList::GetElement(unsigned int n) const { if (n >= current) n = current – 1; // broken if n == 0 return array[n]; } void DList::Print() const { if (current == 0) { cout << “Empty List”; return; } int i; for (i = 0; i < current – 1; i++) // print all but the last cout << array[i] << “, “; cout << array[i]; // print the last int DList::GetSize() const { return current; }

12. main.cpp
#include <iostream> #include “dlist.h” using namespace std; int main() { DList d; cout << “Initial list:\n”; d.Print(); d.Insert(5.4); d.Insert(2.3); d.Insert(10.67); d.Print(); }

13. Exercises Try to add the following member functions to the class
bool Delete(unsigned int index); // delete the specified,
// return true for success, false otherwise
double Sum(); // return the sum of the list elements
double Average(); // return the average of elements
double Max(); // return the max value in the list
void Clear(); // reset the list to empty
int Greater(double x); // return the number of list
// elements that are greater than x

14. Example: Blackjack Card Game Simulation
Multiple classes, using composition relationship
Card objects embedded in the Deck (components)
Deck and Player objects are member data of class Dealer (manager class)
Arrays of objects as member data
Use member data to track array usage
Enumeration usage (suits of the cards)

15. carddeck.h
enum Suit {CLUBS, DIAMONDS, HEARTS, SPADES}; class Card { public: void Display() const; void SetSuit(Suit); void SetVal(int); Suit GetSuite() const; int GetVal() const; private: Suit s; int val; // 2…14, representing 2..10, J, Q, K, A };

16. carddeck.h
class Deck { public: Deck(); void Shuffle(); void ShuffleRest(); // shuffle the undealt cards Card DealCard(); // deal one card from the deck int TopCard() const; private: int topCard; // index of current top card of deck // tracking the current state of the deck Card cards[52]; // notice the composition };

17. carddeck.cpp
#include <iostream> // for cout #include <cstdlib> // for rand(), srand() #include <ctime> // for clock() #include “carddeck.h” using namespace std;

18. carddeck.cpp
void Card::Display() const { if ((2 <= val) && (val <= 10)) cout << val; else { switch(val) { case 11: cout << ‘J’; break; case 12: cout << ‘Q’; break; case 13: cout << ‘K’; break; case 14: cout << ‘A’; break; }

19. carddeck.cpp
switch(s) { case CLUBS: cout << “ of clubs”; break; case DIAMONDS: cout << “ of diamonds”; break; case HEARTS: cout << “ of hearts”; break; case SPADES: cout << “ of spades”; break; } cout << ‘\n’;

20. carddeck.cpp
void Card::SetSuit(Suit suit) { s = suit; } Void Card::SetVal(int v) { val = v; } Suit Card::GetSuit() const { return s; } int Card::GetVal() const { return val; } void Randomize() { unsigned int seed = unsigned(clock()); srand(seed); }

21. carddeck.cpp
Deck::Deck() { topcard = 0; for (int i = 0; i < 52; i++) { cards[i].SetVal((i % 13) + 2); // val = switch(i/13) { case 0: cards[i].SetSuit(CLUBS); case 1: cards[i].SetSuit(DIAMONDS); case 2: cards[i].SetSuite(HEARTS); case 3: cards[i].SetSuit(SPADES); }

22. carddeck.cpp
Deck::Shuffle() { Randomize(); for (int i = 0; i < 3; i++) { // shuffle 3 times for (int j = 0; j < 52; j++) { int r = rand() % 52; Card c = cards[j]; cards[j] = cards[r]; cards[r] = c; } topCard = 0; // no cards dealt yet

23. carddeck.cpp
Deck::ShuffleRest() { Randomize(); for (int i = 0; i < 3; i++) { // shuffle 3 times for (int j = topCard; j < 52; j++) { int r = rand() % (52 – topCard) + topCard; Card c = cards[j]; cards[j] = cards[r]; cards[r] = c; }

24. carddeck.cpp
// yet to error check the exhausted deck Card Deck::DealCard() { Card deal; deal = cards[topCard]; topCard++; return deal; } int Deck::TopCard() const { return topCard; }

25. Variable tracks the number of allocated array slots in use
player.h
#include “carddeck.h” class Player { public: Player(); void ClearHand(); void TakeCard(Card c); int NumCards() const; int GetPot() const; void AddToPot(int val); int HandValue() const; // compute the hand value void ShowHand() const; private: Card hand[5]; int pot; int numCards; };
Variable tracks the number of allocated array slots in use

26. player.cpp
#include <iostream> #include “player.h” using namespace std; Player::Player() { pot = 10; ClearHand(); } void Player()::ClearHand() { numCards = 0; } void Player::TakeCard(Card c) { if (numCards == 5) return; hand[numCards] = c; numCards++; } int Player::NumCards() const { return numCards; }

27. player.cpp
int Player::GetPot() const { return pot; } void Player::AddToPot(int val) { pot += val; } int Player::HandValue() const { int v, total = 0; for (int i = 0; i < numCards; i++) { v = hand[i].GetVal(); if (v <= 10) total += v; else if (v <= 13) total += 10; else total += 11; // for simplicity } return total;

28. Example use of the tracking variable
player.cpp
void Player::ShowHand() const { cout << “\nPLAYER #1’s hand: \n”; for (int i = 0; i < numCards; i++) hand[i].Display(); cout << “*** Total value: “ << HandValue() << ‘\n’; }
Example use of the tracking variable

29. utility.h
int ReadyToQuit(); // return 1 if user enters ‘y’ or ‘Y’ // freeze the screen until the user types a character void WaitForUser();

30. utility.cpp
int ReadyToQuit() { char ans; cout << “\nDo you wish to run the program again (Y for yes, N for no)? “; cin >> ans; ans = toupper(ans); while ((ans != ‘Y’) && (ans != ‘N’)) { cout << “\nPlease answer again with Y or N”; cout << “\n\tRun the program again? “; } return (ans == ‘N’); // returns 1 when ready to quit

31. utility.cpp
void WaitForUser() { cout << “\nPress ‘c’ followed by Enter to continue …”; char any; cin >> any; cout << ‘\n’; }

32. dealer.h
#include “player.h” class Dealer { public: Dealer(); void PlayGame(); void DetermineResults(); private: Player p; // only support one player for now Deck d; Card hand[5]; int numCards;

33. dealer.h
int HandValue(int) const; // compute the hand value // starting with specified card void ShowHand(int) const; // display hand starting // with specified card void Shuflfe(); void DealHand(); // other helper functions void StartHand(); // deal the first 2 cards to each player void DealACardToPlayer(); void DealACardToDealer(); void DealPlayerCards(); void DealDealerCards(); void FindBestHand(); int EndofDeck() const;

34. dealer.cpp
#include <iostream> #include <cctype> // for toupper using namespace std; Dealer::Dealer() { d.Shuffle(); numCards = 0; } void Dealer::PlayGame() { cout << “\n\nGame on!!!\n\n”; do { DealHand(); FindBestHand(); } while (!EndOfDeck()); }

35. dealer.cpp
void Dealer::DetermineResults() { cout << “\n\nPLAYER #1 started with a pot of 10\n”; cout << “*** FINAL POT: “ << p.GetPot() << ‘\n”; } void Dealer::ShowHand(int startCard) const { cout << “\nDealer’s hand: \n”; for (int i = startCard; I < numCards; i++) hand[i].Display(); cout << “*** value showing: “ << HandValue(startCard) << ‘\n’;

36. dealer.cpp
int Dealer::HandValue(int startCard) const { int v, total = 0; for (int i = startCard; i < numCards; i++) { v = hand[i].GetVal(); if (v <= 10) total += v; else if (v <= 13) total += 10; else total += 11; } return total;

37. dealer.cpp
int Dealer::DealHand() { StartHand(); DealPlayerCards(); DealDealerCards(); } void Dealer::StartHand() { p.ClearHand(); numCards = 0; for (int i = 0; i < 2; i++) { DealACardToPlayer(); DealACardToDealer(); p.ShowHand(); ShowHand(1);

38. dealer.cpp
void Dealer::DealACardToPlayer() { p.TakeCard(d.DealCard()); } void Dealer::DealACardToDealer() { hand[numCards++] = d.DealCard();

39. dealer.cpp
void Dealer::DealPlayerCards() { char ans; do { cout << “\nDo you want another card “; cout << “(Y for yes, N for no)? “; cin >> ans; ans = toupper(ans); if (ans == ‘Y’) { DealACardToPlayer(); p.ShowHand(); } } while ((ans == ‘Y’) && (p.HandValue() < 21) && (p.NumCards() <= 5));

40. dealer.cpp
void Dealer::DealDealerCards() { ShowHand(0); while ((HandValue(0) < 17) && (numCards <= 5)) { DealACardToDeader(); ShowHand(0); }

41. dealer.cpp
void Dealder::FindBestHand() { int pVal = p.HandValue(), dVal = HandValue(0); if (((pVal <= 21) && (pVal > dVal)) || (dVal > 21)) { cout << “Player #1 wins hand\n”; p.AddToPot(1); } else if (((dVal <= 21) && (dVal > pVal)) || (pVal > 21)) { cout << “Computer wins hand\n”; p.AddToPot(-1); } else { cout << “Hand was a draw\n”; } WaitForUser();

42. dealer.cpp
// we need (at most) 10 cards int Dealer::EndOfDeck() const { return (d.TopCard() >= 42); }

43. game.cpp
#include <iostream> #include “dealer.h” #include “utility.h” using namespace std; int main() { do { Dealer theDealer; theDealer.PlayGame(); theDealer.DetermineResults(); } while (!ReadyToQuit()); cout << “Goodbye!\n”; return 0; }