Problem with code when trying to amend the Treehouse FunFacts app.

Question

I've been playing around with the FunFacts app, trying to make some changes and get it to do different things. I'm trying to get the text and background colours of the label to change depending on whether the index value of the fun fact pulled from the array is odd or even. I've tried to do that by defining a new method which assigns a colour based on whether the random number generate is odd or even. My problem is that the compiler doesn't recognise 'randomNumber'. I thought that because it's all within the same struct, that it would be within scope. I suspect it's not recognised because it was not 'returned' from the previous method within the struct. Is this correct? Any ideas on how I can make it work? Code copied below.

Thanks for your help. Warren

struct FactProvider {

    var 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 randomFact() -> String {
        let randomNumber = GKRandomSource.sharedRandom().nextInt(upperBound: facts.count)

        return facts[randomNumber]
    }

    func changeColors() {
        let txtColor: UILabel
        let bckColor: UILabel

        if randomNumber % 2 == 0 {
            txtColor.textColor = UIColor.black
            bckColor.backgroundColor = UIColor.white
        } else {
            txtColor.textColor = UIColor.white
            bckColor.backgroundColor = UIColor.black
        }
    }
}

Answer 1 · 2017-05-31T15:56:56Z

May 31, 2017 3:56pm

Hi Warren,

You're correct that randomNumber is out of scope. It exists only within the method where it is created. It isn't returned out of the method, it is just used to set the index of the array.

You can move it so that it is in scope across the whole struct. Move it above the array (or after, but not in a method) but use it in the same way inside the method without creating it again, i.e. don't use let or var again else you'll create another variable of the same name with restricted scope. As you're going to change its value, declare it as a var.

Something like:

struct FactProvider {

    var facts = [
        "Ants stretch when they wake up in the morning.",
        // snip!
    ]

    var randomNumber: Int

    func randomFact() -> String {
        randomNumber = GKRandomSource.sharedRandom().nextInt(upperBound: facts.count)
    // etc

I hope that 1. makes sense and 2. works OK!

Let me know how you get on.

Steve.

Answer 2 · 2017-06-01T07:16:59Z

June 1, 2017 7:16am

Thanks a lot Steve... That does make sense. I'd gone on in the lessons and actually found what I was trying to do - albeit in a very different (and much simpler) way. I will be playing around again today though and will try this. Thanks again for your help. Much appreciated. Warren

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Warren Harding

Warren Harding

Problem with code when trying to amend the Treehouse FunFacts app.

2 Answers

Steve Hunter

Steve Hunter

Warren Harding

Warren Harding

Steve Hunter

Steve Hunter