Swift2 で Alert を表示

MasterViewController.swift

class MasterViewController: UITableViewController {
    ...
    override func viewDidLoad() {
        ...
        let cameraButton = UIBarButtonItem(barButtonSystemItem: UIBarButtonSystemItem.Camera, target: self, action: "doCamera:")
        ...
    }
    ...
    func doCamera(sender: UIButton) {

        // UIAlertControllerを作成する.
        let sampleAlert: UIAlertController = UIAlertController(title: "アラートです", message: "カメラボタン押しました", preferredStyle: .Alert)

        // アクションを作成、追加
        let yesAction = UIAlertAction(title: "OK", style: .Default) { action in print("OK!!") }

        sampleAlert.addAction(yesAction)

        // UIAlertを表示
        self.presentViewController(sampleAlert, animated: true, completion: nil)
    }
}