encapsulating the user code_7.swift

class ViewController: UIViewController
{
    @IBOutlet weak var avatarView: UIImageView!

    var api: API!
    var imagePickerDelegate: ImagePickerDelegate!

    @IBAction func changeAvatar(_ sender: UITapGestureRecognizer) {
        guard let senderView = sender.view else { fatalError("Tapped on viewless gesture recognizer?") }
        
        imagePickerDelegate = ImagePickerDelegate()
        imagePickerDelegate.promise.then { [unowned self] image -> Promise<UIImage> in
            guard let data = UIImageJPEGRepresentation(image, 0.8) else { throw JPEGRepresentationError.badImage }
            return self.api.upload(avatar: data).then { image }
        }
        .then { [unowned self] image in
            self.avatarView.image = image
        }
        .always { [unowned self] in
            self.dismiss(animated: true, completion: nil)
        }
        .catch { [unowned self] error in
            guard error as? UserInteractionError != .userCanceled else { return }
            self.displayInformationAlert(title: "Error", message: error.localizedDescription)
        }
        
        let controller = UIImagePickerController()
        controller.delegate = imagePickerDelegate
        choiceIndexUsingActionSheet(title: "", message: "", choices: sourceOptions.map { $0.title }, onSourceView: senderView).then { index in
            sourceOptions[index].action(controller)
            self.present(controller, animated: true, completion: nil)
        }
    }
}