Swift: display a random array index every button click

Question

I have a swift class that reads lines from a text document and prints out the first line. After, every time a button is clicked a new line is read out.

What I want is to have a random line printed out the first time, and then a random line printed out after every button click.

Here's what I have so far:

import Foundation
import UIKit

class InfoController: UIViewController {

// MARK: Properties
@IBOutlet weak var difficultylevel: UILabel!
var i:Int = 0


override func viewDidLoad() {
    super.viewDidLoad()

}

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

func readFile(){
    if let path = NSBundle.mainBundle().pathForResource("easymath", ofType: "txt"){
        var data = String(contentsOfFile:path, encoding: NSUTF8StringEncoding, error: nil)

        if let content = data {
            let myStrings = content.componentsSeparatedByCharactersInSet(NSCharacterSet.newlineCharacterSet())


            let randomIndex = Int(arc4random_uniform(UInt32(myStrings.count)))
            difficultylevel.text = myStrings[randomIndex]
        }
    }
}



@IBAction func difficultybutton(sender: UIButton) {

    difficultylevel.text = // TODO insert random index of "myStrings" array here

}
}

However, I cannot access the myStrings array at the TODO portion inside the button click. Any help on how to set this up?

Make myStrings a property instead of a local variable (and learn about scope). — matt
– matt, Commented May 25, 2016 at 14:16
You'll also want to call readFile() at some point. Perhaps in viewDidLoad — Charles Caldwell
– Charles Caldwell, Commented May 25, 2016 at 14:20

ColdLogic · Accepted Answer · 2016-05-25 14:33:01Z

Variable scope in Swift is limited to the brackets of the function. So to make myStrings available outside of your readFile() function, you need to declare it as a property for the class:

@IBOutlet var difficultyLevel: UILabel? // BTW your IBOutlet should not be weak
var i: Int = 0
var myStrings: [String]?

Since you are going to use the random functionality over and over, we can abstract the function like this

func randomString() -> String? {
     if let strings = myStrings {
         let randomIndex = Int(arc4random_uniform(UInt32(myStrings.count)))
         return strings[randomIndex]
    }
    return nil
}

then your instantiation will be like this

if let content = data {
    myStrings = content.componentsSeparatedByCharactersInSet(NSCharacterSet.newlineCharacterSet())
    difficultyLevel.text = randomString()
}

Then, your difficultybutton function will be (with an abstracted random string function)

// Changed the name for better readibility
@IBAction func difficultyButtonTapped(sender: UIButton) {
     difficultyLevel.text = randomString()
}

Finally, there isn't any code that calls the readFile function, so you should add it to probably the viewDidLoad function as @CharlesCaldwell points out

override func viewDidLoad() {
     super.viewDidLoad()
     readFile()
}

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