i need help making my practice app.

//
//  ViewController.swift
//  RollMyDice
//
//  Created by Manik Mehta on 8/21/17.
//  Copyright © 2017 Manik Mehta. All rights reserved.
//

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var diceResult: UILabel!

    let onediceResult = oneDice()
    let twodiceResult = twoDice()

    override func viewDidLoad() {
        super.viewDidLoad()

        diceResult.text = "Shake em up & Roll em Dice"

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

    @IBAction func rollOneDice() {
        diceResult.text = onediceResult.oneDiceResult()
    }

    @IBAction func rollTwoDice() {
        diceResult.text = twodiceResult.twoDiceResult()
    }

}

import GameKit

struct oneDice {
let choices = ["One", "Two", "Three", "Four", "Five", "Six"]

func oneDiceResult() -> String {
    let onediceresult = GKRandomSource.sharedRandom().nextInt(upperBound: choices.count)
    return choices[onediceresult]
    }

}

import GameKit

struct twoDice {
let choices2 = ["Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten", "Eleven", "Twelve"]

func twoDiceResult() -> String {
    let twodiceresult = GKRandomSource.sharedRandom().nextInt(upperBound: choices2.count)
    return choices2[twodiceresult]
    }
}