What is 8037?

This is a small mathematical game: you walk down the street and just count the sum of the numbers in the car numbers. We are implementing this game in the console version, in four languages: Swift, Objective-C, Java and C #.

In the first part, we wrote a part of the application that asks the user for an answer until he enters the word to exit the application. As it was reasonably noted in the comments, in this case it would be more correct to use the cycle instead of recursion. Therefore, the first thing we will do is remove the recursion and write a cycle in the startGame method startGame .

Swift:

 func startGame() { var inputWord: String repeat { print(GreetingMessage.replacingOccurrences(of: ExitWordPlaceholder, with: self.exitWord)) inputWord = readLine() ?? "" } while check(inputWord: inputWord) } private func check(inputWord: String) -> Bool { let isExitWord = (inputWord == self.exitWord) print(isExitWord ? GoodByeMessage : InputAcceptMessage.replacingOccurrences(of: InputWordPlaceholder, with: inputWord)) return !isExitWord } 

Objective-C:

 - (void)startGame { NSString *inputWord; do { NSLog(GreetingMessage, self.exitWord); inputWord = [self readLine]; } while ([self checkInputWord:inputWord]); } - (BOOL)checkInputWord:(NSString *)inputWord { BOOL isExitWord = [inputWord isEqualToString:self.exitWord]; isExitWord ? NSLog(@"%@", GoodByeMessage) : NSLog(InputAcceptMessage, inputWord); return !isExitWord; } 

Java:

 void startGame() { String inputWord; do { System.out.println(String.format(GreetingMessage, exitWord)); inputWord = readLine(); } while (checkInputWord(inputWord)); } private boolean checkInputWord(String inputWord) { boolean isExitWord = inputWord.equals(exitWord); System.out.println(isExitWord ? GoodByeMessage : String.format(InputAcceptMessage, inputWord)); return !isExitWord; } 

C #:

 public void startGame() { string inputWord; do { Console.WriteLine(string.Format(GreetingMessage, exitWord)); inputWord = Console.ReadLine(); } while (checkInputWord(inputWord)); } bool checkInputWord(string inputWord) { bool isExitWord = inputWord.Equals(exitWord); Console.WriteLine(isExitWord ? GoodByeMessage : string.Format(InputAcceptMessage, inputWord)); return !isExitWord; } 

Well, then - we finally create a class of our game (as you remember, we specifically created the interface (protocol) Game , which we must implement in our class):

 class Game8037: Game { // MARK: - Game func greet(with exitWord: String) { } func check(userAnswer: String) { } } 

Let's leave the protocol methods empty for now, and let's organize the organization of class functionality. First we need an enum with levels of difficulty:

 private enum Level: String { case easy case normal case hard1 case hard2 func forSelect() -> String { return LevelForSelect.replacingOccurrences(of: LevelPlaceholder, with: self.rawValue) .replacingOccurrences(of: LevelNumberPlaceholder, with: "\(self.hashValue+1)") } } 

We have added the forSelect() method to forSelect() For each level of complexity, it will create a string of type 1 - easy (the level number and its name). This is useful for us to offer the user to choose the level of complexity. Next we need two properties that will contain the selected level and the correct answer to the task:

 private var level: Level private var result: UInt32 

Now we can write our initializer:

 init?() { self.result = 0 let levels = Level.easy.forSelect() + Level.normal.forSelect() + Level.hard1.forSelect() + Level.hard2.forSelect() print(StartGreeting.replacingOccurrences(of: LevelsPlaceholder, with: levels)) let selectedLevel = readLine() ?? "" switch selectedLevel { case "\(Level.easy.hashValue+1)", Level.easy.rawValue: self.level = .easy case "\(Level.normal.hashValue+1)", Level.normal.rawValue: self.level = .normal case "\(Level.hard1.hashValue+1)", Level.hard1.rawValue: self.level = .hard1 case "\(Level.hard2.hashValue+1)", Level.hard2.rawValue: self.level = .hard2 default: print(ErrorLevelMessage) return nil } } 

As you can see, to begin with, we set the default value for the result property (for now, it keeps zero in itself). Next, we form an information line for the user about the need to choose the level of complexity. In the console, it looks like this:

Well and then, we read the level of complexity entered by the user and, if it is correct, we save it in the level property.

Now we need a method for calculating the correct answer to the task depending on the level:

 private func result(with level: Level, and randomizer: Randomizer) -> UInt32 { let result: UInt32 switch level { case .easy: result = randomizer.firstNumber + randomizer.secondNumber + randomizer.thirdNumber + randomizer.fourthNumber case .normal: result = randomizer.firstNumber*10 + randomizer.secondNumber + randomizer.thirdNumber*10 + randomizer.fourthNumber case .hard1: let firstNumber = (randomizer.firstNumber == 0) ? 1 : randomizer.firstNumber let secondNumber = (randomizer.secondNumber == 0) ? 1 : randomizer.secondNumber let thirdNumber = (randomizer.thirdNumber == 0) ? 1 : randomizer.thirdNumber let fourthNumber = (randomizer.fourthNumber == 0) ? 1 : randomizer.fourthNumber result = firstNumber * secondNumber * thirdNumber * fourthNumber case .hard2: result = (randomizer.firstNumber*10 + randomizer.secondNumber) * (randomizer.thirdNumber*10 + randomizer.fourthNumber) } return result } 

And finally, you need to implement the Game protocol methods.
Method greet(with exitWord: String) :

 func greet(with exitWord: String) { let randomizer = Randomizer() self.result = self.result(with: self.level, and: randomizer) let task = BaseGreeting.replacingOccurrences(of: FirstNumberPlaceholder, with: "\(randomizer.firstNumber)") .replacingOccurrences(of: SecondNumberPlaceholder, with: "\(randomizer.secondNumber)") .replacingOccurrences(of: ThirdNumberPlaceholder, with: "\(randomizer.thirdNumber)") .replacingOccurrences(of: FourthNumberPlaceholder, with: "\(randomizer.fourthNumber)") print(TaskMessage.replacingOccurrences(of: TaskPlaceholder, with: task) .replacingOccurrences(of: ExitWordPlaceholder, with: exitWord)) } 

Here we create a new Randomizer and calculate the correct answer for the current level of complexity. Then we show the user the task.

check(userAnswer: String) method check(userAnswer: String) :

 func check(userAnswer: String) { if self.result == UInt32(userAnswer) { print(CorrectMessage) } else { print(WrongMessage) } } 

Everything is simple: we simply compare the correct answer with what the user has entered and display an informational message on the screen.

So the full text of the class in Swift looks like this:

 private let LevelsPlaceholder = "{levels}" private let LevelNumberPlaceholder = "{levelNumber}" private let LevelPlaceholder = "{level}" private let FirstNumberPlaceholder = "{firstNumber}" private let SecondNumberPlaceholder = "{secondNumber}" private let ThirdNumberPlaceholder = "{thirdNumber}" private let FourthNumberPlaceholder = "{fourthNumber}" private let ExitWordPlaceholder = "{exitWord}" private let TaskPlaceholder = "{taskPlaceholder}" private let StartGreeting = "Hello, let's play. Please select difficulty level:\(LevelsPlaceholder)" private let LevelForSelect = "\n\(LevelNumberPlaceholder) - \(LevelPlaceholder)" private let BaseGreeting = "\(FirstNumberPlaceholder) \(SecondNumberPlaceholder) \(ThirdNumberPlaceholder) \(FourthNumberPlaceholder)" private let TaskMessage = "The next task is \(TaskPlaceholder)\n(enter \"\(ExitWordPlaceholder)\" for exit)" private let CorrectMessage = "Absolutely right.\n" private let WrongMessage = "Sorry, you made a mistake. Try again.\n" private let ErrorLevelMessage = "Sorry, you have selected wrong level. Good bye.\n" class Game8037: Game { private enum Level: String { case easy case normal case hard1 case hard2 func forSelect() -> String { return LevelForSelect.replacingOccurrences(of: LevelPlaceholder, with: self.rawValue) .replacingOccurrences(of: LevelNumberPlaceholder, with: "\(self.hashValue+1)") } } private var level: Level private var result: UInt32 init?() { self.result = 0 let levels = Level.easy.forSelect() + Level.normal.forSelect() + Level.hard1.forSelect() + Level.hard2.forSelect() print(StartGreeting.replacingOccurrences(of: LevelsPlaceholder, with: levels)) let selectedLevel = readLine() ?? "" switch selectedLevel { case "\(Level.easy.hashValue+1)", Level.easy.rawValue: self.level = .easy case "\(Level.normal.hashValue+1)", Level.normal.rawValue: self.level = .normal case "\(Level.hard1.hashValue+1)", Level.hard1.rawValue: self.level = .hard1 case "\(Level.hard2.hashValue+1)", Level.hard2.rawValue: self.level = .hard2 default: print(ErrorLevelMessage) return nil } } private func result(with level: Level, and randomizer: Randomizer) -> UInt32 { let result: UInt32 switch level { case .easy: result = randomizer.firstNumber + randomizer.secondNumber + randomizer.thirdNumber + randomizer.fourthNumber case .normal: result = randomizer.firstNumber*10 + randomizer.secondNumber + randomizer.thirdNumber*10 + randomizer.fourthNumber case .hard1: let firstNumber = (randomizer.firstNumber == 0) ? 1 : randomizer.firstNumber let secondNumber = (randomizer.secondNumber == 0) ? 1 : randomizer.secondNumber let thirdNumber = (randomizer.thirdNumber == 0) ? 1 : randomizer.thirdNumber let fourthNumber = (randomizer.fourthNumber == 0) ? 1 : randomizer.fourthNumber result = firstNumber * secondNumber * thirdNumber * fourthNumber case .hard2: result = (randomizer.firstNumber*10 + randomizer.secondNumber) * (randomizer.thirdNumber*10 + randomizer.fourthNumber) } return result } // MARK: - Game func greet(with exitWord: String) { let randomizer = Randomizer() self.result = self.result(with: self.level, and: randomizer) let task = BaseGreeting.replacingOccurrences(of: FirstNumberPlaceholder, with: "\(randomizer.firstNumber)") .replacingOccurrences(of: SecondNumberPlaceholder, with: "\(randomizer.secondNumber)") .replacingOccurrences(of: ThirdNumberPlaceholder, with: "\(randomizer.thirdNumber)") .replacingOccurrences(of: FourthNumberPlaceholder, with: "\(randomizer.fourthNumber)") print(TaskMessage.replacingOccurrences(of: TaskPlaceholder, with: task) .replacingOccurrences(of: ExitWordPlaceholder, with: exitWord)) } func check(userAnswer: String) { if self.result == UInt32(userAnswer) { print(CorrectMessage) } else { print(WrongMessage) } } } 

Implementing the same class in Objective-C:

 //   Game8037.h @interface Game8037 : NSObject <Game> @end //   GameStart.m const NSString *EasyLevelNumber = @"1"; const NSString *NormalLevelNumber = @"2"; const NSString *Hard1LevelNumber = @"3"; const NSString *Hard2LevelNumber = @"4"; const NSString *EasyLevelName = @"easy"; const NSString *NormalLevelName = @"normal"; const NSString *Hard1LevelName = @"hard1"; const NSString *Hard2LevelName = @"hard2"; const NSString *StartGreeting = @"Hello, let's play. Please select difficulty level:%@"; const NSString *LevelForSelect = @"\n%@ - %@"; const NSString *BaseGreeting = @"%i %i %i %i"; const NSString *TaskMessage = @"The next task is %@\n(enter \"%@\" for exit)"; const NSString *CorrectMessage = @"Absolutely right.\n"; const NSString *WrongMessage = @"Sorry, you made a mistake. Try again.\n"; const NSString *ErrorLevelMessage = @"Sorry, you have selected wrong level. Good bye.\n"; typedef enum { LevelEasy, LevelNormal, LevelHard1, LevelHard2 } Level; @interface Game8037() @property (assign, nonatomic) Level level; @property (assign, nonatomic) NSInteger result; @end @implementation Game8037 - (instancetype)init { self = [super init]; if (self) { self.result = 0; NSString *levels = [NSString stringWithFormat:@"%@%@%@%@", [self levelForSelect:LevelEasy], [self levelForSelect:LevelNormal], [self levelForSelect:LevelHard1], [self levelForSelect:LevelHard2]]; NSLog(StartGreeting, levels); NSString *selectedLevel = [self readLine]; if ([selectedLevel isEqualToString:EasyLevelNumber] || [selectedLevel isEqualToString:EasyLevelName]) { self.level = LevelEasy; } else if ([selectedLevel isEqualToString:NormalLevelNumber] || [selectedLevel isEqualToString:NormalLevelName]) { self.level = LevelNormal; } else if ([selectedLevel isEqualToString:Hard1LevelNumber] || [selectedLevel isEqualToString:Hard1LevelName]) { self.level = LevelHard1; } else if ([selectedLevel isEqualToString:Hard2LevelNumber] || [selectedLevel isEqualToString:Hard2LevelName]) { self.level = LevelHard2; } else { NSLog(@"%@", ErrorLevelMessage); return nil; } } return self; } - (NSString *)levelForSelect:(Level)level { NSString *levelNumber; NSString *levelName; switch (level) { case LevelEasy: levelNumber = EasyLevelNumber; levelName = EasyLevelName; break; case LevelNormal: levelNumber = NormalLevelNumber; levelName = NormalLevelName; break; case LevelHard1: levelNumber = Hard1LevelNumber; levelName = Hard1LevelName; break; case LevelHard2: levelNumber = Hard2LevelNumber; levelName = Hard2LevelName; break; } return [NSString stringWithFormat:LevelForSelect, levelNumber, levelName]; } - (NSInteger)resultWithLevel:(Level)level andRandomizer:(Randomizer *)randomizer { NSInteger result = 0; switch (level) { case LevelEasy: result = randomizer.firstNumber + randomizer.secondNumber + randomizer.thirdNumber + randomizer.fourthNumber; break; case LevelNormal: result = randomizer.firstNumber*10 + randomizer.secondNumber + randomizer.thirdNumber*10 + randomizer.fourthNumber; break; case LevelHard1: result = (randomizer.firstNumber == 0 ? 1 : randomizer.firstNumber) * (randomizer.secondNumber == 0 ? 1 : randomizer.secondNumber) * (randomizer.thirdNumber == 0 ? 1 : randomizer.thirdNumber) * (randomizer.fourthNumber == 0 ? 1 : randomizer.fourthNumber); break; case LevelHard2: result = (randomizer.firstNumber*10 + randomizer.secondNumber) * (randomizer.thirdNumber*10 + randomizer.fourthNumber); break; } return result; } - (NSString *)descriptionOfLevel:(Level)level { NSString *result = @""; switch (level) { case LevelEasy: result = EasyLevelName; break; case LevelNormal: result = NormalLevelName; break; case LevelHard1: result = Hard1LevelName; break; case LevelHard2: result = Hard2LevelName; break; } return result; } - (NSString *)readLine { char inputValue; scanf("%s", &inputValue); return [NSString stringWithUTF8String:&inputValue]; } #pragma mark - Game - (void)greetWithExitWord:(NSString *)exitWord { Randomizer *randomizer = [[Randomizer alloc] init]; self.result = [self resultWithLevel:self.level andRandomizer:randomizer]; NSString *task = [NSString stringWithFormat:BaseGreeting, randomizer.firstNumber, randomizer.secondNumber, randomizer.thirdNumber, randomizer.fourthNumber]; NSLog(TaskMessage, task, exitWord); } - (void)checkUserAnswer:(NSString *)userAnswer { if (self.result == [userAnswer integerValue]) { NSLog(@"%@", CorrectMessage); } else { NSLog(@"%@", WrongMessage); } } @end 

Java:

 public class Game8037 implements Game { private static final String EasyLevelNumber = "1"; private static final String NormalLevelNumber = "2"; private static final String Hard1LevelNumber = "3"; private static final String Hard2LevelNumber = "4"; private static final String EasyLevelName = "easy"; private static final String NormalLevelName = "normal"; private static final String Hard1LevelName = "hard1"; private static final String Hard2LevelName = "hard2"; private static final String StartGreeting = "Hello, let's play. Please select difficulty level:%s"; private static final String LevelForSelect = "\n%s - %s"; private static final String BaseGreeting = "%s %s %s %s"; private static final String TaskMessage = "The next task is %s\n(enter \"%s\" for exit)"; private static final String CorrectMessage = "Absolutely right.\n"; private static final String WrongMessage = "Sorry, you made a mistake. Try again.\n"; private static final String ErrorLevelMessage = "Sorry, you have selected wrong level. Good bye.\n"; private enum Level { Easy { public String toString() { return EasyLevelName; } }, Normal { public String toString() { return NormalLevelName; } }, Hard1 { public String toString() { return Hard1LevelName; } }, Hard2 { public String toString() { return Hard2LevelName; } } } private Level level; private int result; private Game8037(Level level) { this.level = level; this.result = 0; } @Nullable public static Game8037 Create() { String levels = String.format("%s%s%s%s", levelForSelect(Level.Easy), levelForSelect(Level.Normal), levelForSelect(Level.Hard1), levelForSelect(Level.Hard2)); System.out.println(String.format(StartGreeting, levels)); Game8037 game8037; String selectedLevel = readLine(); switch (selectedLevel) { case EasyLevelNumber: case EasyLevelName: game8037 = new Game8037(Level.Easy); break; case NormalLevelNumber: case NormalLevelName: game8037 = new Game8037(Level.Normal); break; case Hard1LevelNumber: case Hard1LevelName: game8037 = new Game8037(Level.Hard1); break; case Hard2LevelNumber: case Hard2LevelName: game8037 = new Game8037(Level.Hard2); break; default: game8037 = null; System.out.println(ErrorLevelMessage); break; } return game8037; } private static String levelForSelect(Level level) { String levelNumber = ""; String levelName = ""; switch (level) { case Easy: levelNumber = EasyLevelNumber; levelName = EasyLevelName; break; case Normal: levelNumber = NormalLevelNumber; levelName = NormalLevelName; break; case Hard1: levelNumber = Hard1LevelNumber; levelName = Hard1LevelName; break; case Hard2: levelNumber = Hard2LevelNumber; levelName = Hard2LevelName; break; } return String.format(LevelForSelect, levelNumber, levelName); } private int resultWithLevelAndRandomizer(Level level, Randomizer randomizer) { int result = 0; switch (level) { case Easy: result = randomizer.firstNumber + randomizer.secondNumber + randomizer.thirdNumber + randomizer.fourthNumber; break; case Normal: result = randomizer.firstNumber*10 + randomizer.secondNumber + randomizer.thirdNumber*10 + randomizer.fourthNumber; break; case Hard1: int firstNumber = (randomizer.firstNumber == 0) ? 1 : randomizer.firstNumber; int secondNumber = (randomizer.secondNumber == 0) ? 1 : randomizer.secondNumber; int thirdNumber = (randomizer.thirdNumber == 0) ? 1 : randomizer.thirdNumber; int fourthNumber = (randomizer.fourthNumber == 0) ? 1 : randomizer.fourthNumber; result = firstNumber * secondNumber * thirdNumber * fourthNumber; break; case Hard2: result = (randomizer.firstNumber*10 + randomizer.secondNumber) * (randomizer.thirdNumber*10 + randomizer.fourthNumber); break; } return result; } static private String readLine() { java.util.Scanner scanner = new java.util.Scanner(System.in); return scanner.next(); } @Override public void greet(String exitWord) { Randomizer randomizer = new Randomizer(); result = resultWithLevelAndRandomizer(level, randomizer); String task = String.format(BaseGreeting, randomizer.firstNumber, randomizer.secondNumber, randomizer.thirdNumber, randomizer.fourthNumber); System.out.println(String.format(TaskMessage, task, exitWord)); } @Override public void checkUserAnswer(String userAnswer) { int answer; try { answer = Integer.parseInt(userAnswer); } catch (Exception e) { System.out.println(WrongMessage); return; } if (result == answer) { System.out.println(CorrectMessage); } else { System.out.println(WrongMessage); } } } 

C #:

 public class Game8037 : IGame { const string EasyLevelNumber = "1"; const string NormalLevelNumber = "2"; const string Hard1LevelNumber = "3"; const string Hard2LevelNumber = "4"; const string EasyLevelName = "easy"; const string NormalLevelName = "normal"; const string Hard1LevelName = "hard1"; const string Hard2LevelName = "hard2"; const string StartGreeting = "Hello, let's play. Please select difficulty level:{0}"; const string LevelForSelect = "\n{0} - {1}"; const string BaseGreeting = "{0} {1} {2} {3}"; const string TaskMessage = "The next task is {0}\n(enter \"{1}\" for exit)"; const string CorrectMessage = "Absolutely right.\n"; const string WrongMessage = "Sorry, you made a mistake. Try again.\n"; const string ErrorLevelMessage = "Sorry, you have selected wrong level. Good bye.\n"; enum Level { Easy, Normal, Hard1, Hard2 }; Level level; int result; private Game8037(Level level) { this.level = level; result = 0; } public static Game8037 Create() { string levels = string.Format("{0}{1}{2}{3}", levelForSelect(Level.Easy), levelForSelect(Level.Normal), levelForSelect(Level.Hard1), levelForSelect(Level.Hard2)); Console.WriteLine(string.Format(StartGreeting, levels)); Game8037 game8037; string selectedLevel = Console.ReadLine(); switch (selectedLevel) { case EasyLevelNumber: case EasyLevelName: game8037 = new Game8037(Level.Easy); break; case NormalLevelNumber: case NormalLevelName: game8037 = new Game8037(Level.Normal); break; case Hard1LevelNumber: case Hard1LevelName: game8037 = new Game8037(Level.Hard1); break; case Hard2LevelNumber: case Hard2LevelName: game8037 = new Game8037(Level.Hard2); break; default: game8037 = null; Console.WriteLine(ErrorLevelMessage); break; } return game8037; } static string levelForSelect(Level level) { string levelNumber = ""; string levelName = ""; switch (level) { case Level.Easy: levelNumber = EasyLevelNumber; levelName = EasyLevelName; break; case Level.Normal: levelNumber = NormalLevelNumber; levelName = NormalLevelName; break; case Level.Hard1: levelNumber = Hard1LevelNumber; levelName = Hard1LevelName; break; case Level.Hard2: levelNumber = Hard2LevelNumber; levelName = Hard2LevelName; break; } return string.Format(LevelForSelect, levelNumber, levelName); } int resultWithLevelAndRandomizer(Level level, Randomizer randomizer) { int result = 0; switch (level) { case Level.Easy: result = randomizer.firstNumber + randomizer.secondNumber + randomizer.thirdNumber + randomizer.fourthNumber; break; case Level.Normal: result = randomizer.firstNumber * 10 + randomizer.secondNumber + randomizer.thirdNumber * 10 + randomizer.fourthNumber; break; case Level.Hard1: int firstNumber = (randomizer.firstNumber == 0) ? 1 : randomizer.firstNumber; int secondNumber = (randomizer.secondNumber == 0) ? 1 : randomizer.secondNumber; int thirdNumber = (randomizer.thirdNumber == 0) ? 1 : randomizer.thirdNumber; int fourthNumber = (randomizer.fourthNumber == 0) ? 1 : randomizer.fourthNumber; result = firstNumber* secondNumber * thirdNumber * fourthNumber; break; case Level.Hard2: result = (randomizer.firstNumber * 10 + randomizer.secondNumber) * (randomizer.thirdNumber * 10 + randomizer.fourthNumber); break; } return result; } string descriptionOfLevel(Level level) { string result = ""; switch (level) { case Level.Easy: result = "easy"; break; case Level.Normal: result = "normal"; break; case Level.Hard1: result = "hard1"; break; case Level.Hard2: result = "hard2"; break; } return result; } public void greet(string exitWord) { Randomizer randomizer = new Randomizer(); result = resultWithLevelAndRandomizer(level, randomizer); string task = string.Format(BaseGreeting, randomizer.firstNumber, randomizer.secondNumber, randomizer.thirdNumber, randomizer.fourthNumber); Console.WriteLine(string.Format(TaskMessage, task, exitWord)); } public void checkUserAnswer(string userAnswer) { int answer; try { answer = int.Parse(userAnswer); } catch { Console.WriteLine(WrongMessage); return; } if (result == answer) { Console.WriteLine(CorrectMessage); } else { Console.WriteLine(WrongMessage); } } } 

In Java and C #, there is a nuance when creating an object of the Game8037 class. The fact is that there are no failable initializers, so we used the static method to create an object.

It remains for us to add the creation of our game to the GameStart class and use the methods greet(...) and check(...) . Now the GameStart class looks like this.

Swift:

 class GameStart { private var exitWord: String private var game: Game init?(with exitWord: String) { self.exitWord = exitWord if let game = Game8037() { self.game = game } else { return nil } } func startGame() { var inputWord: String repeat { self.game.greet(with: self.exitWord) inputWord = readLine() ?? "" } while check(inputWord: inputWord) } private func check(inputWord: String) -> Bool { let isExitWord = (inputWord == self.exitWord) if isExitWord { print(GoodByeMessage) } else { self.game.check(userAnswer: inputWord) } return !isExitWord } } 

Objective-C:

 @interface GameStart() @property (strong, nonatomic) NSString *exitWord; @property (strong, nonatomic) id<Game> game; @end @implementation GameStart - (instancetype)initWithExitWord:(NSString *)exitWord { self = [super init]; if (self) { self.exitWord = exitWord; self.game = [[Game8037 alloc] init]; } return self; } - (void)startGame { if (self.game) { NSString *inputWord; do { [self.game greetWithExitWord:self.exitWord]; inputWord = [self readLine]; } while ([self checkInputWord:inputWord]); } } - (BOOL)checkInputWord:(NSString *)inputWord { BOOL isExitWord = [inputWord isEqualToString:self.exitWord]; if (isExitWord) { NSLog(@"%@", GoodByeMessage); } else { [self.game checkUserAnswer:inputWord]; } return !isExitWord; } - (NSString *)readLine { char inputValue; scanf("%s", &inputValue); return [NSString stringWithUTF8String:&inputValue]; } @end 

Java:

 public class GameStart { private static final String GreetingMessage = "Please enter your answer (enter \"%s\" for exit):"; private static final String InputAcceptMessage = "You entered \"%s\".\n"; private static final String GoodByeMessage = "Good bye.\n"; private String exitWord; private Game game; public GameStart(String exitWord) { this.exitWord = exitWord; this.game = Game8037.Create(); } void startGame() { if (game != null) { String inputWord; do { game.greet(exitWord); inputWord = readLine(); } while (checkInputWord(inputWord)); } } private boolean checkInputWord(String inputWord) { boolean isExitWord = inputWord.equals(exitWord); if (isExitWord) { System.out.println(GoodByeMessage); } else { game.checkUserAnswer(inputWord); } return !isExitWord; } private String readLine() { java.util.Scanner scanner = new java.util.Scanner(System.in); return scanner.next(); } } 

C #:

 public class GameStart { const string GreetingMessage = "Please enter your answer (enter \"{0}\" for exit):"; const string InputAcceptMessage = "You entered \"{0}\".\n"; const string GoodByeMessage = "Good bye.\n"; readonly string exitWord; readonly IGame iGame; public GameStart(string exitWord) { this.exitWord = exitWord; iGame = Game8037.Create(); } public void startGame() { if (iGame != null) { string inputWord; do { iGame.greet(exitWord); inputWord = Console.ReadLine(); } while (checkInputWord(inputWord)); } } bool checkInputWord(string inputWord) { bool isExitWord = inputWord.Equals(exitWord); if (isExitWord) { Console.WriteLine(GoodByeMessage); } else { iGame.checkUserAnswer(inputWord); } return !isExitWord; } } 

As you can see, we have added a game property of type Game (or IGame in C #). We also call self.game.greet(...) in the startGame() method, and self.game.greet(...) in the check(...) method. Thus, in the future, it will be Game8037 substitute any other game that implements our Game protocol instead of Game8037 .

Conclusion

This is the end of the work on our application, the source code of all this can be found here . Thank you all for your attention, comments, criticism, advice, suggestions. :)