In Chapter 8, you created a basic bookstore iPhone app with Swift. In this chapter, you will add some features to the app to make it a bit more functional and use many of the technologies you have learned in this book, such as creating a class, using delegates and protocols, and using actions and outlets. You’ll also learn about some new techniques such as switches, UIAlertViewController, and landmarks.

Let’s Get Started

The bookstore example in Chapter 8 enabled you to view books in your bookstore in a TableView and then tap the book to see its details. In this chapter, you will add the following capabilities to the Chapter 8 bookstore app:

• Adding a book
• Deleting a book
• Modifying a book

See Figures 14-1 and 14-2.

Using the app you created in Chapter 8, add a Button Bar item by dragging the Button Bar Item object to the right button bar location in the Main.storyboard file. Change the Button Bar item’s title to Add. This will change the button bar’s title to Add, as shown in Figure 14-3.

Modify and add the code that will handle a showDetail method and a addBookSegue segue in the MasterViewController.swift file, starting at line 51 in Listing 14-1. The code will transition to the scene that will add a book to the list and pass the view to a delegate. The next step is to define the AddBookViewController.

40  // MARK: - Segues
41
42 override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
43         if segue.identifier == "showDetail" {
44             if let indexPath = self.tableView.indexPathForSelectedRow {
45                 let selectedBook:Book = myBookStore.theBookStore[indexPath.row]
46                 let vc = segue.destinationViewController as! DetailViewController
47                 vc.detailItem = selectedBook
48                 vc.delegate = self
49             }
50         }
51         else if segue.identifier == "addBookSegue" {
52             let vc = segue.destinationViewController as! AddBookViewController
53             vc.delegate = self
54         }
55     }

Now add the new view controller AddBookViewController mentioned in line 52 in Listing 14-1. Add a View Controller object to the storyboard by dragging a View Controller to the Main.storyboard file. Then add the objects in Figure 14-5 to enable the user to add a new book. Feel free to move the scenes around to make it clear how they relate to each other, as shown in Figure 14-5.

Add a Push Segue object from the Add Button Bar item to the new View Controller by Control-dragging dragging or right-clicking and dragging from the Add Button Bar item to the new View Controller, as shown Figure 14-6.

Label the Segue object by clicking the segue arrow and labeling the identifier as addBookSegue, as shown in Figure 14-7.

Now you need to create a Swift class to go with the new View Controller. Create a new file and Cocoa class and name it AddBookViewController, as shown in Figure 14-8. Make sure you select a subclass of UIViewController.

Now you have to associate the new AddBookViewController class to the new View Controller. Select the View Controller, and in the Identity Inspector, type AddBookViewController for the class, as shown in Figure 14-9.

Set the title of the view to Add Book by double-clicking on the Navigation Bar. Open the AddBookViewController.swift file and add the code shown in Listing 14-2.

9 import UIKit
10
11 protocol BookStoreDelegate {
12     func newBook(controller: AnyObject, newBook: Book)
13     func editBook(controller: AnyObject, editBook: Book)
14     func deleteBook(controller: AnyObject)
15 }
16
17
18 class AddBookViewController: UIViewController {
19     var book = Book()
20     var delegate: BookStoreDelegate? = nil
21     var read = false
22     var editBook = false
23
24     @IBOutlet weak var titleText: UITextField!
25     @IBOutlet weak var authorText: UITextField!
26     @IBOutlet weak var pagesText: UITextField!
27     @IBOutlet weak var switchOutlet: UISwitch!
28
29     @IBOutlet weak var descriptionText: UITextView!
30
31
32     override func viewDidLoad() {
33         super.viewDidLoad()
34         if(editBook == true){
35             self.title = "Edit Book"
36             titleText.text = book.title
37             authorText.text = book.author
38             pagesText.text = String(book.pages)
39             descriptionText.text = book.description
40             if (book.readThisBook){
41                 switchOutlet.on = true
42             }
43             else {
44                switchOutlet.on = false
45             }
46         }
47
48     }
49
50     override func didReceiveMemoryWarning() {
51         super.didReceiveMemoryWarning()
52         // Dispose of any resources that can be recreated.
53     }
54
55
56     @IBAction func saveBookAction(sender: UIButton) {
57         book.title = titleText.text!
58         book.author = authorText.text!
59         book.description = descriptionText.text
60         book.pages = Int(pagesText.text!)!
61         if(switchOutlet.on) {
62           book.readThisBook = true
63         }
64         else {
65           book.readThisBook = false
66         }
67         if (editBook) {
68             delegate!.editBook(self, editBook:book)
69         }
70         else {
71             delegate!.newBook(self, newBook:book)
72         }
73     }
74 }

To the Book class, add two properties: pages and readThisBook. These are shown in lines 15 and 16 in Listing 14-3.

11 class Book {
12     var title: String = ""
13     var author: String = ""
14     var description: String = ""
15     var pages: Int = 0
16     var readThisBook: Bool = false
17 }

Switches

Connect the outlets in the AddBookViewController class by dragging them from their open circles to the controls, as shown in Figure 14-10.

Connect the saveBookAction action by dragging the outlet circle to the Save Book button, as shown in Figure 14-11.

In the DetailViewController class, add the code shown in Listing 14-4.

20    @IBOutlet weak var pagesOutlet: UILabel!
21    @IBOutlet weak var switchOutlet: UISwitch!
22
23     var delegate: BookStoreDelegate? = nil

24
25     var myBook = Book()

Alert View Controllers

Add the controls for Pages, Read, and Edit for the DetailViewController. Connect the outlets by dragging the open circles to their controls, as shown in Figure 14-12.

The Read switch is disabled in this view by unchecking the Enabled property in the Attributes Inspector.

Add the code for displaying an AlertViewController when the Delete Button Bar is tapped, as shown in Listing 14-5.

52 @IBAction func deleteBookAction(sender: UIBarButtonItem) {
53         let alertController = UIAlertController(title: "Warning", message: "Delete this book?",            preferredStyle: .Alert)
54         let noAction = UIAlertAction(title: "No", style: .Cancel) { (action) in
55             print("Cancel")
56         }
57         alertController.addAction(noAction)
58
59         let yesAction = UIAlertAction(title: "Yes", style: .Destructive) { (action) in
60            self.delegate!.deleteBook(self)
61         }
62         alertController.addAction(yesAction)
63
64         self.presentViewController(alertController, animated: false, completion: nil)
65     }

Add the Delete Button Bar item to the right navigation location and connect it to the action, as shown in Figure 14-13.

The UIAlertViewController will warn the user that the book currently displayed in the DetailViewController is about to be deleted and will enable the user to decide whether to delete it. The UIAlertViewController has two buttons: Yes and No. When the user taps the Delete right Button Bar item, the UIAlertViewController will be as shown, in Figure 14-14, when you are done.

When the user taps Yes to delete the book, you want to call a deleteBook delegate method as described in the MasterViewController class. You add the delegate property that will store the MasterViewController view in Listing 14-6.

11 class MasterViewController: UITableViewController, BookStoreDelegate {

Let’s now talk about the three delegate methods: newBook, deleteBook, and editBook, as defined in the AddBookViewController class in Listing 14-2 (lines 11 to 15). Add these three functions at the end MasterViewController class, as shown in Listing 14-7.

91 // MARK: - Delegate Methods conforming to the BookStoreDelegate as defined in the                AddBookViewController
 92     func newBook(controller: AnyObject, newBook: Book) {
 93         myBookStore.theBookStore.append(newBook)
 94         self.tableView.reloadData()
 95         let myController = controller as! AddBookViewController
 96         myController.navigationController?.popToRootViewControllerAnimated(true)
 97     }
 98
 99     func deleteBook(controller: AnyObject){
100         let indexPath = self.tableView.indexPathForSelectedRow
101         var row = indexPath?.row
102         myBookStore.theBookStore.removeAtIndex(row!)
103         self.tableView.reloadData()
104         let myController = controller as! DetailViewController
105         myController.navigationController?.popToRootViewControllerAnimated(true)
106     }
107
108     func editBook(controller: AnyObject, editBook: Book){
109         let indexPath = self.tableView.indexPathForSelectedRow
110         var row = indexPath?.row
111         myBookStore.theBookStore.insert(editBook, atIndex: row!)
112         myBookStore.theBookStore.removeAtIndex(row! + 1)
113         self.tableView.reloadData()
114         let myController = controller as! AddBookViewController
115         myController.navigationController?.popToRootViewControllerAnimated(true)
116     }

The function newBook adds a new book to the bookstore; appending the array with the newBook does this, as shown in line 93. Line 94 then reloads the Table view by calling all the Table view delegate methods:

numberOfSectionsInTableView
numberOfRowsInSection
cellForRowAtIndexPath

Finally, you pop the DetailViewController from the navigation stack by calling popToRootViewControllerAnimated(true). Popping the view from the navigation stack means the view is removed similarly to tapping the Back button.

The function deleteBook removes the book from the bookStore array. First you determine which row was selected in the tableView and use that index to delete the book in the array by calling removeAtIndex(row!), as shown on line 102.

The function editBook enables the user to edit an existing book in the bookStore array. To do this, the function inserts the edited book in the array at the row that was selected, as shown on line 111. Then the function deletes the original book that was pushed down one index when you inserted the book in the array, as shown on line 112.

Now add the Edit button to the bottom of the DetailViewController and add a Show Segue object from the edit button to the AddBookViewController, as shown in Figure 14-15.

Select the Segue object you just created, select the Attributes Inspector, and name the identifier editDetail. See Figure 14-16.

Add the prepareForSegue function shown in Listing 14-8 to the bottom of the DetailViewController.swift file.

81 override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
82         if segue.identifier == "editDetail" {
83             let vc = segue.destinationViewController as! AddBookViewController
84             vc.delegate = delegate
85             vc.editBook = true
86             vc.book = myBook
87         }
88     }

Finally, modify the configureView function in the DetailViewController to properly populate the pages and switch outlets, as shown in Listing 14-9.

29  func configureView() {
30     if let detail: AnyObject = self.detailItem {
31         myBook = detail as! Book
32         titleLabel.text = myBook.title
33         authorLabel.text = myBook.author
34         descriptionTextView.text = myBook.description
35         pagesOutlet.text = String(myBook.pages)
36         if(myBook.readThisBook){
37              switchOutlet.on = true
38          }
39          else {
40               switchOutlet.on = false
41           }
42        }
43     }

App Summary

Compile and run the app. You should set breakpoints at the delegate functions to watch the program flow. It is a great app to see how delegates can be used to pass information from one view to another.

Additionally, you can add functionality to the app to make the information persistent by using Core Data or NSUserDefaults.

Exercises

• Add more books to the bookstore using the original program as a guide.
• Enhance the Book class so it can store another attribute—a price or ISBN, for example.
• Add persistence to the app by using Core Data or NSUserDefaults.