Question

I am generating a random number between 0 and topOfRange. I can exclude firstNumberToExclude with this code:

NSInteger aRandom;
while ((aRandom = arc4random()%topOfRange) == firstNumberToExclude);

how about if I had two numbers to exclude: firstNumberToExclude and secondNumberToExclude? This was my plan but doesnt seem to be proper:

NSInteger aRandom = arc4random()%topOfRange;
while (aRandom == firstNumberToExclude || aRandom == secondNumberToExclude)
    {
    aRandom = arc4random()%topOfRange;
    }

Answer 1

I think your code would be cleaner, and easier to maintain, if you refactored this into a utility method:

+ (NSInteger)generateRandomExcluding:(NSArray *)exclude topOfRange:(NSInteger)topOfRange {
    NSInteger aRandom = arc4random_uniform(topOfRange);
    while ([exclude containsObject:[NSNumber numberWithInteger:aRandom]]) {
        aRandom = arc4random_uniform(topOfRange);
    }
    return aRandom;
}

Then you can call it like:

NSNumber *excludeOne = [NSNumber numberWithInt:5];
NSNumber *excludeTwo = [NSNumber numberWithInt:13];

NSInteger random = [MyClass generateRandomExcluding:[NSArray arrayWithObjects:excludeOne, excludeTwo, nil] topOfRange:100];