Creating a random color to a label that does not appear twice

Question

I am working on my first project where I am trying to create a random color to a UILabel (when a button is pressed) that does not repeat itself twice in a row. I have read many questions and found codes that generates random numbers that does not appear twice in a row, however, when I "link" that random number to a UIColor and "link" that UIColor to a label the code no longer works. This code has no errors but it allows the same color to appear twice;

@IBOutlet var HelloWorld: UILabel!
@IBOutlet var MyButton: UIButton!

@IBAction func MyButton(sender: AnyObject) {
let randomNumber2 = Int(arc4random_uniform(5))

    if randomNumber2 == 0 {
        HelloWorld.textColor = UIColor.redColor()
    }
    else if randomNumber2 == 1 {
        HelloWorld.textColor = UIColor.blueColor()
    }
    else if randomNumber2 == 2 {
        HelloWorld.textColor = UIColor.yellowColor()
    }
    else if randomNumber2 == 3 {
        HelloWorld.textColor = UIColor.orangeColor()
    }
    else if randomNumber2 == 4 {
        HelloWorld.textColor = UIColor.blueColor()
    }

Does anyone know how to generate a random color to a label that does not appear twice in a row?

Answer 1

You can use this Singleton class

class ColorGenerator {
    static let sharedInstance = ColorGenerator()
    private var last: UIColor
    private var colors: [UIColor] = [.redColor(), .blueColor(), .yellowColor(), .orangeColor(), .greenColor()]

    private init() {
        let random = Int(arc4random_uniform(UInt32(colors.count)))
        self.last = colors[random]
        colors.removeAtIndex(random)
    }

    func next() -> UIColor {
        let random = Int(arc4random_uniform(UInt32(colors.count)))
        swap(&colors[random], &last)
        return last
    }
}

The usage is pretty straightforward

Step 1

Create a new file in your project ColorGenerator.swift and paste the code above into it.

Step 2

Anywhere in your code just write

ColorGenerator.sharedInstance.next()

to get a new random UIColor.

That's it.