ViewController.swift

import UIKit

class ViewController: UIViewController {

    @IBOutlet var loginButton: UIButton!
    var accountsList:[Dictionary<String,String>]?
    var tweets:[Dictionary<String, AnyObject>]?

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

        self.navigationItem.title = "Login"
        accountsList = [["name":"Hiro"], ["name":"Jeff"], ["name":"Chris"]]
    }

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

    @IBAction func tappedLoginButton(sender: AnyObject) {
        var accountSelectionSheet = UIAlertController()
        accountSelectionSheet.title = "Select Account"

        let selectAction =  { (var action: UIAlertAction!) -> Void in
            self.performSegueWithIdentifier("showTimelineViewController", sender: nil)
        }

        if let accounts:[Dictionary<String, String>] = accountsList{
            for account in accounts {
                let action = UIAlertAction(title: account["name"]!, style: .Default, handler: selectAction)
                accountSelectionSheet.addAction(action)
            }
        }

        let CanceledAction = UIAlertAction(title: "Cancel", style: .Cancel, handler: nil)
        accountSelectionSheet.addAction(CanceledAction)

        self.presentViewController(accountSelectionSheet, animated: true, completion: nil)
    }

}