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iOS Objective-C Basics Practicing with Immersive Examples Immersive example 1 - Ping-Pong

Objective-C variable

My code is as follows:

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[]) {

    //Nate vs Kyle
    //first to 21 or more win by 2
    //print winner

    int kyleScore = 0;
    int nateScore = 0;

    bool gamePlaying = YES;

    int pointWinner;

    int winTwentyOne = 21;
    int winByTwo = ((kyleScore - nateScore >= 2) || (nateScore - kyleScore >= 2));

    NSString *gameWinner;

    while(gamePlaying) {

        pointWinner = arc4random()%2;

        (pointWinner == 0) ? kyleScore++ : nateScore++;

        if ((kyleScore >= winTwentyOne || nateScore >= winTwentyOne) && ((kyleScore - nateScore >= 2) || (nateScore - kyleScore >= 2))) {

            gameWinner = (kyleScore > nateScore) ? @"Kyle" : @"Nate";
            gamePlaying = NO;
        }

    }

    NSLog(@"%@ is the winner!", gameWinner);

    return 0;
}

This code works. I am curious, however, why if instead I use

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[]) {

    //Nate vs Kyle
    //first to 21 or more win by 2
    //print winner

    int kyleScore = 0;
    int nateScore = 0;

    bool gamePlaying = YES;

    int pointWinner;

    int winTwentyOne = 21;
    int winByTwo = ((kyleScore - nateScore >= 2) || (nateScore - kyleScore >= 2));

    NSString *gameWinner;

    while(gamePlaying) {

        pointWinner = arc4random()%2;

        (pointWinner == 0) ? kyleScore++ : nateScore++;

        if ((kyleScore >= winTwentyOne || nateScore >= winTwentyOne) && winByTwo) {

            gameWinner = (kyleScore > nateScore) ? @"Kyle" : @"Nate";
            gamePlaying = NO;
        }

    }

    NSLog(@"%@ is the winner!", gameWinner);

    return 0;
}

does not. All I changed was used winByTwo rather than typing it all into the last if statement.

Build succeeds however I get no output.

Thank you !

2 Answers

Nathan Tallack
Nathan Tallack
22,158 Points

In your version you are no longer evaluating the winByTwo with each loop through the while. You are just using the result of that one evaluation before you entered the while loop.

If you do want to keep the evaluation seperate to your if conditional inside the loop at least move the winByTwo evaluation into the while loop so that it can keep getting updated with each iteration of the loop.

Thank you Nathan ! Figured it out last night and forgot to update. Either way I appreciate it :)

Marleen Berg
Marleen Berg
22,524 Points

Maybe if people are curious, I think this is the most shortest way to complete this challenge.. not written by me, but maybe it is nice to open a topic where people can post their answer to learn from others?

it is not the most readable code, the for loop isn't used like is should be, but the output is fine...

int main(int argc, const char * argv[]) {
    int pp1 = 0, pp2 = 0, ws = 21;
    for(int i = 0; pp1 != ws && pp2 != ws; i++){
        int j = arc4random()%2;
        pp1 = j == 0 ? pp1 + 1 : pp1;
        pp2 = j == 1 ? pp2 + 1 : pp2;
        if(pp1 == ws || pp2 == ws)
            NSLog(pp1 == ws ? @"Player 1 wins" : pp2 == ws ? @"Player 2 wins" : @"");
    }