Calling different extent of randomness of arc4random in Swift?

Question

This might be rather stupid question. I would like to know if different nuances/extent of randomness would be possible using arc4random_uniform in Swift. Here's an example:

let number = arc4random_uniform(10) + 1
print(number)

In this case, a number will be printed randomly from 1 to 10. But is there a way that I can repeat the random result, 2 to 3 times? The result would be something like this:

1, 1, 6, 6, 6, 3, 3, 8, 8, 9, 9, 9 ...

// 1) Randomly selected and 2) repeated 2 to 3 times randomly.

Perhaps I might use two arc4random_uniform functions together, but cannot express them properly. Would be much appreciated if you could give me some suggestions. <3

Answer 1

In order to do this, you will need to generate two values: your random value and a repeatCount. Also, you'll need to remember both of those values so that you can repeat the value. You can do this with a custom class:

class RandomWithRepeats {
    var range: ClosedRange<Int>
    var repeatRange: ClosedRange<Int>
    var repeatCount = 0
    var value = 0

    init(range: ClosedRange<Int>, repeatRange: ClosedRange<Int>) {
        self.range = range
        self.repeatRange = repeatRange
    }

    // generate a random number in a range
    // Just use Int.random(in:) with Swift 4.2 and later
    func random(in range: ClosedRange<Int>) -> Int {
        return Int(arc4random_uniform(UInt32(range.upperBound - range.lowerBound + 1))) + range.lowerBound
    }

    func nextValue() -> Int {
        // if repeatCount is 0, its time to generate a new value and
        // a new repeatCount
        if repeatCount == 0 {
            // For Swift 4.2, just use Int.random(in:) instead
            value = self.random(in: range)
            repeatCount = self.random(in: repeatRange)
        }

        repeatCount -= 1
        return value
    }
}

Example:

let rand = RandomWithRepeats(range: 1...10, repeatRange: 2...3)

// generate 20 random repeated numbers    
for _ in 1...20
{
    print(rand.nextValue(), terminator: " ")
}

6 6 6 8 8 8 10 10 10 2 2 9 9 5 5 8 8 8 5 5