How Do I Prevent Same Random Color and Random Fact From Showing Consecutively in Swift?

Question

I have completed the Build a Simple iPhone App with Swift course at Treehouse, and now I would like to add a feature to it. I want to prevent the same background color and same interesting fact from showing consecutively. I have been working on this, but I just cannot seem to figure out the correct way. I tried storing a randomIndex variable in FactBook.swift and ColorWheel.swift to hold the random numbers generated to get the random fact/color. Then I used a do-while loop to compare that random number with the variable and generate another random number if they matched. However, I was not able to get the scope correct in the loop.

Here is my code that I have for the project so far:

ViewController.swift

    import UIKit

    class ViewController: UIViewController {

    @IBOutlet weak var funFactLabel: UILabel!
    @IBOutlet weak var funFactButton: UIButton!

    let factBook = FactBook()
    let colorWheel = ColorWheel()

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        funFactLabel.text = factBook.randomFact()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    @IBAction func showFunFact() {
        var randomColor = colorWheel.randomColor()
        view.backgroundColor = randomColor
        funFactButton.tintColor = randomColor
        funFactLabel.text = factBook.randomFact()
    }

}

FactBook.swift

import Foundation

struct FactBook {

    var randomIndex = 0

    let factsArray = [
        "Ants stretch when they wake up in the morning.",
        "Ostritches can run faster than horses.",
        "Olympic gold medals are actually mostly made 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 the Earth.",
        "Some bamboo plants can grow almost a meter in just one day.",
        "Some penguins can leap 2-3 meters out of the water.",
        "The state of Florida is bigger than England.",
        "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 {
        var unsignedArrayCount = UInt32(factsArray.count)
        var unsignedRandomNumber = arc4random_uniform(unsignedArrayCount)
        var randomNumber = Int(unsignedRandomNumber)

        // verify value of randomNumber
        println(randomNumber)

        return factsArray[randomNumber]
    }

}

ColorWheel.swift

import Foundation
import UIKit

struct ColorWheel {
    let colorsArray = [
        UIColor(red: 90/255.0, green: 187/255.0, blue: 181/255.0, alpha: 1.0), //teal color
        UIColor(red: 222/255.0, green: 171/255.0, blue: 66/255.0, alpha: 1.0), //yellow color
        UIColor(red: 223/255.0, green: 86/255.0, blue: 94/255.0, alpha: 1.0), //red color
        UIColor(red: 239/255.0, green: 130/255.0, blue: 100/255.0, alpha: 1.0), //orange color
        UIColor(red: 77/255.0, green: 75/255.0, blue: 82/255.0, alpha: 1.0), //dark color
        UIColor(red: 105/255.0, green: 94/255.0, blue: 133/255.0, alpha: 1.0), //purple color
        UIColor(red: 85/255.0, green: 176/255.0, blue: 112/255.0, alpha: 1.0), //green color
    ]

    func randomColor() -> UIColor {
        var unsignedArrayCount = UInt32(colorsArray.count)
        var unsignedRandomNumber = arc4random_uniform(unsignedArrayCount)
        var randomNumber = Int(unsignedRandomNumber)

        return colorsArray[randomNumber]
    }
}

Answer 1

Make mutable copies of your two arrays and use those mutable arrays as your working arrays. After you select a random element in those arrays, delete that member. When the count goes to zero, make a new copy if you want to keep going.