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iOS

Every 10th time the button is pressed the label doesn't change, why?

Using the same code as in the video, every tenth time the button is pressed the label doesn't change. Does this have to do with the way the random number is generated using GameKit?

The question is related to the video "Finishing Up Our Model" in the "Build a Simple iPhone App with Swift 2.0" course.

Here is the object that wherein the method "getRandomFact" uses GameKit to supply a random fact.

struct FactModel {
    let facts = [
        "Ants stretch when they wake up in the morning.",
        "Ostriches can run faster than horses.",
        "Olympic gold medals are actually made mostly of silver.",
        "You are born with 300 bones; by the time you are an adult you will have 206.",
        "It takes about 8 minutes for light from the Sun to reach Earth.",
        "Some bamboo plants can grow almost a meter in just one day.",
        "The state of Florida is bigger than England.",
        "Some penguins can leap 2-3 meters out of the water.",
        "On average, it takes 66 days to form a new habit.",
        "Mammoths still walked the Earth when the Great Pyramid was being built." ]

    func getRandomFact() -> String {
        let randomNumber = GKRandomSource.sharedRandom().nextIntWithUpperBound(facts.count)

        return facts[randomNumber]
    }
}
Kyle Lambert
Kyle Lambert
1,969 Points

I had the same problem when building this app. I believe it is because the random number generator will sometimes choose the same number two or more times in a row. If this occurs, the fact will not change until a different index number is randomly chosen.

Hope this helps Marco

1 Answer

Jari Koopman
seal-mask
.a{fill-rule:evenodd;}techdegree seal-36
Jari Koopman
Python Web Development Techdegree Graduate 29,349 Points

Hi Marco,

I just tested my old project of this course, we used code that's a little different (see below)

func randomFact() -> String {
        var unsignedArrayCount = UInt32(factsArray.count)
        var unsignedRandomNumber = arc4random_uniform(unsignedArrayCount)
        var randomNumber = Int(unsignedRandomNumber)

        return factsArray[randomNumber]
    }

But I get the same "problem" that it doesn't change on the 10th click. I think it's something in the way the random number is chosen.

I used this:

var chosenFact: String?
    var retrunedFact: String!


    func randomFactGenerator(currentFact: String) -> String {
        factGenerator()
        while chosenFact == currentFact {
            factGenerator()
        }

        if let factChosen = chosenFact {
            retrunedFact = factChosen
        }

        return retrunedFact
    }

    func factGenerator() {
        let arrayCount = UInt32(factsArray.count)
        let unasignedRandomNumber = arc4random_uniform(arrayCount)
        let randomNumber = Int(unasignedRandomNumber)

        chosenFact = factsArray[randomNumber]

    }

in another project of mine. To call call the randomFactGenerator method with as parameter the current text propperty of the label like this: randomFactGenerator(textLabel.text)

Hope this helped!

Kind regards, Jari

I'll have a look. Thank you...