rainbow.swift

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var BtnView: UIButton!
    
    var index = 0
    var colors =
        [UIColor(red: 1, green: 0, blue: 0, alpha: 1),
        UIColor(red: 1, green: 127/255, blue: 0, alpha: 1),
        UIColor(red: 1, green: 1, blue: 0, alpha: 1),
        UIColor(red: 0, green: 1, blue: 0, alpha: 1),
        UIColor(red: 0, green: 0, blue: 1, alpha: 1),
        UIColor(red: 75/255, green: 0, blue: 130/255, alpha: 1),
        UIColor(red: 148/255, green: 0, blue: 211/255, alpha: 1)]
    
    @IBAction func Btn(_ sender: Any) {
        
        view.backgroundColor = colors[index]
        update()
        if index == colors.count{
            index = 0
        }
    }
   
    func update(){
        
        index = index + 1
        
    }
    
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        
        index = Int(arc4random_uniform(7))
        view.backgroundColor = colors[index]  //隨機產生array裡的顏色
        
        // Do any additional setup after loading the view, typically from a nib.
    }