Copyright (C) 2016 Apple Inc. All Rights Reserved.
    See LICENSE.txt for this sample’s licensing information
    A 'Table View Controller' subclass that displays the data for an existing Person or for creating a new Person in the app. This class is also responsible for creating a new person to update in the PeopleTableViewController when the done button is tapped.
    Customizations: Whenever you want to add new data about a Person, you will want to add in  appropriate interface elements in the Main.storyboard and have those interface elements updated in this class to display and edit the data. To learn more you  can check out the the README file included in the app.
import UIKit
class PersonViewController: UITableViewController, UITextFieldDelegate {
    // MARK: Properties
        When editing an existing person, this value is passed by 
        PeopleTableViewController in 'prepareForSegue(segue: sender:)'.
    var person: Person?
    @IBOutlet weak var doneButton: UIBarButtonItem!
    @IBOutlet weak var nameTextField: UITextField!
    @IBOutlet weak var imageButton: UIButton!
    @IBOutlet weak var preferenceSlider: UISlider!
    override func viewDidLoad() {
        // Set up the views if editing an existing person.
        if let person = person {
            nameTextField.text =
            imageButton.setImage(person.image, for: [])
                If they have a dog preference value set, update the slider, 
                otherwise it will use the default value set in the Main.storyboard 
            if let dogPreference = person.dogPreference {
                preferenceSlider.value = dogPreference
    // MARK: Navigation
    @IBAction func cancelTapped(_ sender: UIBarButtonItem) {
            Depending on style of presentation, this view controller needs to be 
            dismissed in two different ways. We used a modal presentation for 
            adding people, which needs to be dismissed. Editing an existing person 
            used a 'push', which requires a 'pop' to return to the previous page.
        let isPresentingInAddMode = presentingViewController is UINavigationController
        if isPresentingInAddMode {
            dismiss(animated: true, completion: nil)
        else {
            navigationController!.popViewController(animated: true)
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        // Only update the person if the done button was tapped.
        if let sender = sender as? UIBarButtonItem!, sender === doneButton {
            let name = nameTextField.text
            let image = imageButton.image(for: [])
            let dogPreference = preferenceSlider.value
                Create and set the person to be passed to PeopleTableViewController 
                after the unwind segue.
            person = Person(name: name, image: image, dogPreference: dogPreference)
    // MARK: UITextFieldDelegate
        When the user hits the return or "Done" button on a text field, we want 
        the keyboard to go away.
    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        return true