how to open the Photo Library on iPhone

this is the minimum.

import UIKit

class ViewController: UIViewController, UIImagePickerControllerDelegate ,UINavigationControllerDelegate{

    @IBAction func openPhotoLibrary(sender: UIButton) {

        var photoPicker = UIImagePickerController()

        photoPicker.delegate = self

        photoPicker.sourceType = .PhotoLibrary

        

        self.presentViewController( photoPicker, animated: true, completion: nil)

        

    }

@https://www.youtube.com/watch?v=leyk3QOYJF0


complete ver of this instruction video
import UIKit

class ViewController: UIViewController, UIImagePickerControllerDelegate ,UINavigationControllerDelegate{

    

    var photoImageView = UIImageView(frame: CGRectMake(40, 120, 200, 200))

    

    @IBAction func openPhotoLibrary(sender: UIButton) {
        var photoPicker = UIImagePickerController()
        photoPicker.delegate = self
        photoPicker.sourceType = .PhotoLibrary

        

        self.presentViewController( photoPicker, animated: true, completion: nil)

        

    }

   override func viewDidLoad() {
        super.viewDidLoad()

        self.view.addSubview(photoImageView)

    

        // Do any additional setup after loading the view, typically from a nib.

    }

    override func didReceiveMemoryWarning() {

        super.didReceiveMemoryWarning()

        // Dispose of any resources that can be recreated.

   }

    

    func imagePickerController(picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [NSObject: AnyObject]) {

        

        photoImageView.image = info [UIImagePickerControllerOriginalImage]as? UIImage

        self.dismissViewControllerAnimated(false, completion: nil)

    }

}