You are previewing iOS 6 Programming Cookbook.

iOS 6 Programming Cookbook

Cover of iOS 6 Programming Cookbook by Vandad Nahavandipoor Published by O'Reilly Media, Inc.
  1. iOS 6 Programming Cookbook
  2. Preface
    1. Audience
    2. Organization of This Book
    3. Additional Resources
    4. Conventions Used in This Book
    5. Using Code Examples
    6. We’d Like to Hear from You
    7. Safari® Books Online
    8. Acknowledgments
  3. 1. The Basics
    1. 1.0. Introduction
    2. 1.1. Creating a Simple iOS App in Xcode
      1. Problem
      2. Solution
      3. Discussion
    3. 1.2. Understanding Interface Builder
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    4. 1.3. Compiling iOS Apps
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    5. 1.4. Running iOS Apps on the Simulator
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    6. 1.5. Running iOS Apps on iOS Devices
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    7. 1.6. Packaging iOS Apps for Distribution
      1. Problem
      2. Solution
      3. Discussion
    8. 1.7. Declaring Variables in Objective-C
      1. Problem
      2. Solution
      3. Discussion
    9. 1.8. Allocating and Making Use of Strings
      1. Problem
      2. Solution
      3. Discussion
    10. 1.9. Comparing Values in Objective-C with an if Statement
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    11. 1.10. Implementing Loops with for Statements
      1. Problem
      2. Solution
      3. Discussion
    12. 1.11. Implementing while Loops
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    13. 1.12. Creating Custom Classes
      1. Problem
      2. Solution
      3. Discussion
    14. 1.13. Defining Functionality for Classes
      1. Problem
      2. Solution
      3. Discussion
    15. 1.14. Defining Two or More Methods with the Same Name
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    16. 1.15. Allocating and Initializing Objects
      1. Problem
      2. Solution
      3. Discussion
    17. 1.16. Adding Properties to Classes
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    18. 1.17. Moving from Manual Reference Counting to Automatic Reference Counting
      1. Problem
      2. Solution
      3. Discussion
    19. 1.18. Typecasting with Automatic Reference Counting
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    20. 1.19. Delegating Tasks with Protocols
      1. Problem
      2. Solution
      3. Discussion
    21. 1.20. Determining Whether Instance or Class Methods Are Available
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    22. 1.21. Determining Whether a Class Is Available at Runtime
      1. Problem
      2. Solution
      3. Discussion
    23. 1.22. Allocating and Making Use of Numbers
      1. Problem
      2. Solution
      3. Discussion
    24. 1.23. Allocating and Making Use of Arrays
      1. Problem
      2. Solution
      3. Discussion
    25. 1.24. Allocating and Making Use of Dictionaries
      1. Problem
      2. Solution
      3. Discussion
    26. 1.25. Allocating and Making Use of Sets
      1. Problem
      2. Solution
      3. Discussion
    27. 1.26. Creating Bundles
      1. Problem
      2. Solution
      3. Discussion
    28. 1.27. Loading Data from the Main Bundle
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    29. 1.28. Loading Data from Other Bundles
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    30. 1.29. Sending Notifications with NSNotificationCenter
      1. Problem
      2. Solution
      3. Discussion
    31. 1.30. Listening for Notifications Sent from NSNotificationCenter
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
  4. 2. Implementing Controllers and Views
    1. 2.0. Introduction
    2. 2.1. Displaying Alerts with UIAlertView
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    3. 2.2. Creating and Using Switches with UISwitch
      1. Problem
      2. Solution
      3. Discussion
    4. 2.3. Customizing the UISwitch
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    5. 2.4. Picking Values with UIPickerView
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    6. 2.5. Picking the Date and Time with UIDatePicker
      1. Problem
      2. Solution
      3. Discussion
    7. 2.6. Implementing Range Pickers with UISlider
      1. Problem
      2. Solution
      3. Discussion
    8. 2.7. Customizing the UISlider
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    9. 2.8. Grouping Compact Options with UISegmentedControl
      1. Problem
      2. Solution
      3. Discussion
    10. 2.9. Customizing the UISegmentedControl
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    11. 2.10. Presenting and Managing Views with UIViewController
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    12. 2.11. Presenting Sharing Options with UIActivityViewController
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    13. 2.12. Implementing Navigation with UINavigationController
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    14. 2.13. Manipulating a Navigation Controller’s Array of View Controllers
      1. Problem
      2. Solution
      3. Discussion
    15. 2.14. Displaying an Image on a Navigation Bar
      1. Problem
      2. Solution
      3. Discussion
    16. 2.15. Adding Buttons to Navigation Bars Using UIBarButtonItem
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    17. 2.16. Presenting Multiple View Controllers with UITabBarController
      1. Problem
      2. Solution
      3. Discussion
    18. 2.17. Displaying Static Text with UILabel
      1. Problem
      2. Solution
      3. Discussion
    19. 2.18. Customizing the UILabel
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    20. 2.19. Accepting User Text Input with UITextField
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    21. 2.20. Displaying Long Lines of Text with UITextView
      1. Problem
      2. Solution
      3. Discussion
    22. 2.21. Adding Buttons to the User Interface with UIButton
      1. Problem
      2. Solution
      3. Discussion
    23. 2.22. Displaying Images with UIImageView
      1. Problem
      2. Solution
      3. Discussion
    24. 2.23. Creating Scrollable Content with UIScrollView
      1. Problem
      2. Solution
      3. Discussion
    25. 2.24. Loading Web Pages with UIWebView
      1. Problem
      2. Solution
      3. Discussion
    26. 2.25. Presenting Master-Detail Views with UISplitViewController
      1. Problem
      2. Solution
      3. Discussion
    27. 2.26. Enabling Paging with UIPageViewController
      1. Problem
      2. Solution
      3. Discussion
    28. 2.27. Displaying Popovers with UIPopoverController
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    29. 2.28. Displaying Progress with UIProgressView
      1. Problem
      2. Solution
      3. Discussion
    30. 2.29. Listening and Reacting to Keyboard Notifications
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    31. 2.30. Constructing and Displaying Styled Texts
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
  5. 3. Auto Layout and the Visual Format Language
    1. 3.0. Introduction
    2. 3.1. Placing UI Components in the Center of the Screen
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    3. 3.2. Defining Horizontal and Vertical Constraints with the Visual Format Language
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    4. 3.3. Utilizing Cross View Constraints
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    5. 3.4. Configuring Auto Layout Constraints in Interface Builder
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
  6. 4. Constructing and Using Table Views
    1. 4.0. Introduction
    2. 4.1. Instantiating a Table View
      1. Problem
      2. Solution
      3. Discussion
    3. 4.2. Assigning a Delegate to a Table View
      1. Problem
      2. Solution
      3. Discussion
    4. 4.3. Populating a Table View with Data
      1. Problem
      2. Solution
      3. Discussion
    5. 4.4. Receiving and Handling Table View Events
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    6. 4.5. Using Different Types of Accessories in a Table View Cell
      1. Problem
      2. Solution
      3. Discussion
    7. 4.6. Creating Custom Table View Cell Accessories
      1. Problem
      2. Solution
      3. Discussion
    8. 4.7. Displaying Hierarchical Data in Table Views
      1. Problem
      2. Solution
      3. Discussion
    9. 4.8. Enabling Swipe Deletion of Table View Cells
      1. Problem
      2. Solution
      3. Discussion
    10. 4.9. Constructing Headers and Footers in Table Views
      1. Problem
      2. Solution
      3. Discussion
    11. 4.10. Displaying Context Menus on Table View Cells
      1. Problem
      2. Solution
      3. Discussion
    12. 4.11. Moving Cells and Sections in Table Views
      1. Problem
      2. Solution
      3. Discussion
    13. 4.12. Deleting Cells and Sections from Table Views
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    14. 4.13. Utilizing the UITableViewController for Easy Creation of Table Views
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    15. 4.14. Displaying a Refresh Control for Table Views
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
  7. 5. Storyboards
    1. 5.0. Introduction
    2. 5.1. Creating a Project with Storyboards
      1. Problem
      2. Solution
      3. Discussion
    3. 5.2. Adding a Navigation Controller to a Storyboard
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    4. 5.3. Passing Data From One Screen to Another
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    5. 5.4. Adding a Storyboard to an Existing Project
      1. Problem
      2. Solution
      3. Discussion
  8. 6. Concurrency
    1. 6.0. Introduction
    2. 6.1. Constructing Block Objects
      1. Problem
      2. Solution
      3. Discussion
    3. 6.2. Accessing Variables in Block Objects
      1. Problem
      2. Solution
      3. Discussion
    4. 6.3. Invoking Block Objects
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    5. 6.4. Dispatching Tasks to Grand Central Dispatch
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    6. 6.5. Performing UI-Related Tasks with GCD
      1. Problem
      2. Solution
      3. Discussion
    7. 6.6. Executing Non-UI Related Tasks Synchronously with GCD
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    8. 6.7. Executing Non-UI Related Tasks Asynchronously with GCD
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    9. 6.8. Performing Tasks After a Delay with GCD
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    10. 6.9. Performing a Task Only Once with GCD
      1. Problem
      2. Solution
      3. Discussion
    11. 6.10. Grouping Tasks Together with GCD
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    12. 6.11. Constructing Your Own Dispatch Queues with GCD
      1. Problem
      2. Solution
      3. Discussion
    13. 6.12. Running Tasks Synchronously with Operations
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    14. 6.13. Running Tasks Asynchronously with Operations
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    15. 6.14. Creating Dependency Between Operations
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    16. 6.15. Creating Timers
      1. Problem
      2. Solution
      3. Discussion
    17. 6.16. Creating Concurrency with Threads
      1. Problem
      2. Solution
      3. Discussion
    18. 6.17. Invoking Background Methods
      1. Problem
      2. Solution
      3. Discussion
    19. 6.18. Exiting Threads and Timers
      1. Problem
      2. Solution
      3. Discussion
  9. 7. Core Location and Maps
    1. 7.0. Introduction
    2. 7.1. Creating a Map View
      1. Problem
      2. Solution
      3. Discussion
    3. 7.2. Handling the Events of a Map View
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    4. 7.3. Pinpointing the Location of a Device
      1. Problem
      2. Solution
      3. Discussion
    5. 7.4. Displaying Pins on a Map View
      1. Problem
      2. Solution
      3. Discussion
    6. 7.5. Displaying Pins with Different Colors on a Map View
      1. Problem
      2. Solution
      3. Discussion
    7. 7.6. Displaying Custom Pins on a Map View
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    8. 7.7. Converting Meaningful Addresses to Longitude and Latitude
      1. Problem
      2. Solution
      3. Discussion
    9. 7.8. Converting Longitude and Latitude to a Meaningful Address
      1. Problem
      2. Solution
      3. Discussion
  10. 8. Implementing Gesture Recognizers
    1. 8.0. Introduction
    2. 8.1. Detecting Swipe Gestures
      1. Problem
      2. Solution
      3. Discussion
    3. 8.2. Detecting Rotation Gestures
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    4. 8.3. Detecting Panning and Dragging Gestures
      1. Problem
      2. Solution
      3. Discussion
    5. 8.4. Detecting Long Press Gestures
      1. Problem
      2. Solution
      3. Discussion
    6. 8.5. Detecting Tap Gestures
      1. Problem
      2. Solution
      3. Discussion
    7. 8.6. Detecting Pinch Gestures
      1. Problem
      2. Solution
      3. Discussion
  11. 9. Networking, JSON, XML, and Twitter
    1. 9.0. Introduction
    2. 9.1. Downloading Asynchronously with NSURLConnection
      1. Problem
      2. Solution
      3. Discussion
    3. 9.2. Handling Timeouts in Asynchronous Connections
      1. Problem
      2. Solution
      3. Discussion
    4. 9.3. Downloading Synchronously with NSURLConnection
      1. Problem
      2. Solution
      3. Discussion
    5. 9.4. Modifying a URL Request with NSMutableURLRequest
      1. Problem
      2. Solution
      3. Discussion
    6. 9.5. Sending HTTP GET Requests with NSURLConnection
      1. Problem
      2. Solution
      3. Discussion
    7. 9.6. Sending HTTP POST Requests with NSURLConnection
      1. Problem
      2. Solution
      3. Discussion
    8. 9.7. Sending HTTP DELETE Requests with NSURLConnection
      1. Problem
      2. Solution
      3. Discussion
    9. 9.8. Sending HTTP PUT Requests with NSURLConnection
      1. Problem
      2. Solution
      3. Discussion
    10. 9.9. Serializing Arrays and Dictionaries into JSON
      1. Problem
      2. Solution
      3. Discussion
    11. 9.10. Deserializing JSON into Arrays and Dictionaries
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    12. 9.11. Integrating Twitter Functionality into Your Apps
      1. Problem
      2. Solution
      3. Discussion
    13. 9.12. Parsing XML with NSXMLParser
      1. Problem
      2. Solution
      3. Discussion
  12. 10. Audio and Video
    1. 10.0. Introduction
    2. 10.1. Playing Audio Files
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    3. 10.2. Handling Interruptions while Playing Audio
      1. Problem
      2. Solution
      3. Discussion
    4. 10.3. Recording Audio
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    5. 10.4. Handling Interruptions while Recording Audio
      1. Problem
      2. Solution
      3. Discussion
    6. 10.5. Playing Audio over Other Active Sounds
      1. Problem
      2. Solution
      3. Discussion
    7. 10.6. Playing Video Files
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    8. 10.7. Capturing Thumbnails from a Video File
      1. Problem
      2. Solution
      3. Discussion
    9. 10.8. Accessing the Music Library
      1. Problem
      2. Solution
      3. Discussion
  13. 11. Address Book
    1. 11.0. Introduction
    2. 11.1. Requesting Access to the Address Book
      1. Problem
      2. Solution
      3. Discussion
    3. 11.2. Retrieving a Reference to an Address Book
      1. Problem
      2. Solution
      3. Discussion
    4. 11.3. Retrieving All the People in the Address Book
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    5. 11.4. Retrieving Properties of Address Book Entries
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    6. 11.5. Inserting a Person Entry into the Address Book
      1. Problem
      2. Solution
      3. Discussion
    7. 11.6. Inserting a Group Entry into the Address Book
      1. Problem
      2. Solution
      3. Discussion
    8. 11.7. Adding Persons to Groups
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    9. 11.8. Searching the Address Book
      1. Problem
      2. Solution
      3. Discussion
    10. 11.9. Retrieving and Setting a Person’s Address Book Image
      1. Problem
      2. Solution
      3. Discussion
  14. 12. Files and Folder Management
    1. 12.0. Introduction
    2. 12.1. Finding the Paths of the Most Useful Folders on Disk
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    3. 12.2. Writing to and Reading from Files
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    4. 12.3. Creating Folders on Disk
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    5. 12.4. Enumerating Files and Folders
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    6. 12.5. Deleting Files and Folders
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    7. 12.6. Securing Files on Disk
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    8. 12.7. Saving Objects to Files
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
  15. 13. Camera and the Photo Library
    1. 13.0. Introduction
    2. 13.1. Detecting and Probing the Camera
      1. Problem
      2. Solution
      3. Discussion
    3. 13.2. Taking Photos with the Camera
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    4. 13.3. Taking Videos with the Camera
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    5. 13.4. Storing Photos in the Photo Library
      1. Problem
      2. Solution
      3. Discussion
    6. 13.5. Storing Videos in the Photo Library
      1. Problem
      2. Solution
      3. Discussion
    7. 13.6. Retrieving Photos and Videos from the Photo Library
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    8. 13.7. Retrieving Assets from the Assets Library
      1. Problem
      2. Solution
      3. Discussion
    9. 13.8. Editing Videos on an iOS Device
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
  16. 14. Multitasking
    1. 14.0. Introduction
    2. 14.1. Detecting the Availability of Multitasking
      1. Problem
      2. Solution
      3. Discussion
    3. 14.2. Completing a Long-Running Task in the Background
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    4. 14.3. Receiving Local Notifications in the Background
      1. Problem
      2. Solution
      3. Discussion
    5. 14.4. Playing Audio in the Background
      1. Problem
      2. Solution
      3. Discussion
    6. 14.5. Handling Location Changes in the Background
      1. Problem
      2. Solution
      3. Discussion
    7. 14.6. Saving and Loading the State of Multitasking iOS Apps
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    8. 14.7. Handling Network Connections in the Background
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    9. 14.8. Handling Notifications Delivered to a Waking App
      1. Problem
      2. Solution
      3. Discussion
    10. 14.9. Responding to Changes in App Settings
      1. Problem
      2. Solution
      3. Discussion
    11. 14.10. Opting Out of Multitasking
      1. Problem
      2. Solution
      3. Discussion
  17. 15. Core Data
    1. 15.0. Introduction
    2. 15.1. Creating a Core Data Model with Xcode
      1. Problem
      2. Solution
      3. Discussion
    3. 15.2. Generating Class Files for Core Data Entities
      1. Problem
      2. Solution
      3. Discussion
    4. 15.3. Creating and Saving Data Using Core Data
      1. Problem
      2. Solution
      3. Discussion
    5. 15.4. Reading Data from Core Data
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    6. 15.5. Deleting Data from Core Data
      1. Problem
      2. Solution
      3. Discussion
    7. 15.6. Sorting Data in Core Data
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    8. 15.7. Boosting Data Access in Table Views
      1. Problem
      2. Solution
      3. Discussion
    9. 15.8. Implementing Relationships in Core Data
      1. Problem
      2. Solution
      3. Discussion
  18. 16. Dates, Calendars, and Events
    1. 16.0. Introduction
    2. 16.1. Retrieving the List of Calendars
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    3. 16.2. Adding Events to Calendars
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    4. 16.3. Accessing the Contents of Calendars
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    5. 16.4. Removing Events from Calendars
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    6. 16.5. Adding Recurring Events to Calendars
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    7. 16.6. Retrieving the Attendees of an Event
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    8. 16.7. Adding Alarms to Calendars
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    9. 16.8. Handling Event Changed Notifications
      1. Problem
      2. Solution
      3. Discussion
    10. 16.9. Presenting Event View Controllers
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    11. 16.10. Presenting Event Edit View Controllers
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
  19. 17. Graphics and Animations
    1. 17.0. Introduction
    2. 17.1. Enumerating and Loading Fonts
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    3. 17.2. Drawing Text
      1. Problem
      2. Solution
      3. Discussion
    4. 17.3. Constructing, Setting, and Using Colors
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    5. 17.4. Drawing Images
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    6. 17.5. Constructing Resizable Images
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    7. 17.6. Drawing Lines
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    8. 17.7. Constructing Paths
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    9. 17.8. Drawing Rectangles
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    10. 17.9. Adding Shadows to Shapes
      1. Problem
      2. Solution
      3. Discussion
    11. 17.10. Drawing Gradients
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    12. 17.11. Displacing Shapes Drawn on Graphic Contexts
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    13. 17.12. Scaling Shapes Drawn on Graphic Contexts
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    14. 17.13. Rotating Shapes Drawn on Graphic Contexts
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    15. 17.14. Animating and Moving Views
      1. Problem
      2. Solution
      3. Discussion
    16. 17.15. Animating and Scaling Views
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    17. 17.16. Animating and Rotating Views
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
  20. 18. Core Motion
    1. 18.0. Introduction
    2. 18.1. Detecting the Availability of an Accelerometer
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    3. 18.2. Detecting the Availability of a Gyroscope
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    4. 18.3. Retrieving Accelerometer Data
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    5. 18.4. Detecting Shakes on an iOS Device
      1. Problem
      2. Solution
      3. Discussion
    6. 18.5. Retrieving Gyroscope Data
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
  21. 19. iCloud
    1. 19.0. Introduction
    2. 19.1. Setting Up Your App for iCloud
      1. Problem
      2. Solution
      3. Discussion
    3. 19.2. Storing and Synchronizing Dictionaries in iCloud
      1. Problem
      2. Solution
      3. Discussion
    4. 19.3. Creating and Managing Folders for Apps in iCloud
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    5. 19.4. Searching for Files and Folders in iCloud
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    6. 19.5. Storing User Documents in iCloud
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    7. 19.6. Managing the State of Documents in iCloud
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    8. 19.7. Handling Conflicts in iCloud Documents
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
  22. 20. Pass Kit
    1. 20.0. Introduction
    2. 20.1. Creating Pass Kit Certificates
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    3. 20.2. Creating Pass Files
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    4. 20.3. Providing Icons and Images for Passes
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    5. 20.4. Preparing Your Passes for Digital Signature
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    6. 20.5. Signing Passes Digitally
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    7. 20.6. Distributing Passes Using Email
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    8. 20.7. Distributing Passes Using Web Services
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    9. 20.8. Enabling Your iOS Apps to Access Passes on iOS Devices
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
    10. 20.9. Interacting with Passbook Programmatically
      1. Problem
      2. Solution
      3. Discussion
      4. See Also
  23. Index
  24. About the Author
  25. Colophon
  26. Copyright
O'Reilly logo

1.23. Allocating and Making Use of Arrays

Problem

You want to store a series of objects into another object for later use.

Solution

Use NSArray and NSMutableArray classes to store objects into arrays that are fixed and that you can change, respectively.

Discussion

An object of type NSArray or any of its subclasses has the capability to store n number of other objects, where n will be determined by the runtime and is influenced by how much memory is available at the time. These objects can then be accessed using their index. For instance, let’s say you have 10 pairs of socks. Now imagine placing them all on a flat surface from left to right and calling them socks 1, socks 2, socks 3, and so on. So the leftmost pair of socks is now addressed as socks 1, the pair next to it is called socks 2, and the rightmost pair is called socks 10. Isn’t that easier than saying something like “the blue socks next to my red socks”? That’s exactly what arrays do: they make arranging items much easier.

Note

You can place any object of type NSObject or any of its subclasses into an array of type NSArray (or subclasses of that type). An array can contain a mix of different types of objects. Not all objects have to be of the same type. In other words, you can have one array with strings, numbers, dictionaries, or even other arrays inside it. Arrays can contain any object as long as those objects can be wrapped in the id data type wrapper.

The primary difference between NSArray and NSMutableArray is that a mutable array can be changed/modified after it has been allocated and initialized, whereas an immutable array, NSArray, cannot.

Let’s have a look at an example. First, create an instance of NSString and two instances of NSNumber and place them in an immutable array:

NSArray *array = @[@"My String", @123, @-123];
NSLog(@"array = %@", array);

When you run this program, the following text is printed to your console:

array = (
    "My String",
    123,
    "-123"
)

We used the new collection subscripting features of our LLVM compiler to construct the array. These let us construct the array using the @[] collection format and place our objects between the opening and the closing square brackets. This syntax creates an instance of an array for us. When using this method of constructing your arrays, pass your objects that need to be placed inside the array one by one.

We can also use the arrayWithObjects: class method of NSArray to create an autorelease array, like so:

NSArray *array = [NSArray arrayWithObjects:
                  stringObject,
                  signedNumber,
                  unsignedNumber, nil];

You can call the count method on your array to get the number of objects in that array. You can go through your array using a for loop or using an enumerator. Let’s have a look at the solution with a for loop first:

NSArray *array = @[@"My String", @123, @-123];

NSUInteger counter = 0;
for (counter = 0;
     counter < [array count];
     counter++){

    id object = array[counter];
    NSLog(@"Object = %@", object);

}

And here is the output:

Object = My String
Object = -123
Object = 123

Aside from the [] syntax to access a specific object in an array, we can also use the objectAtIndex: method to get an object at a specific index. Remember that indexes are zero based. In other words, when the counter reaches -1, the loop has to stop because there can be no negative indexes in an array.

As mentioned before, you can also use fast enumeration to go through objects of an array. Fast enumeration is a language feature in Objective-C that allows you to enumerate objects in an array or dictionary (or any other object that supports fast enumeration) without having to use any counter or for loop. The format is as follows:

for (Type variableName in array/dictionary/etc){ ... }

Suppose we want to code the previous example without the overhead of a counter variable. Here is how we can do it using fast enumeration:

for (id object in array){
    NSLog(@"Object = %@", object);
  }

The results are practically identical to the results we got from the previous version of this code that used a counter variable.

Mutable arrays are very interesting. As you probably have already guessed, immutable arrays cannot be modified once allocated and initialized. Mutable arrays, however, can be modified after their allocation and initialization. Let’s have a look at an example:

NSArray *anotherArray = @[@"String 1", @"String 2", @"String 3"];

NSMutableArray *mutableArray = [NSMutableArray arrayWithArray:
                                @[@"My String", @123, @-123]];

[mutableArray addObject:@123];
[mutableArray removeObject:@-123];
[mutableArray addObjectsFromArray:anotherArray];

for (id object in mutableArray){
    NSLog(@"Object = %@", object);
}

Before we go into analyzing the code, let’s have a look at its output:

Object = My String
Object = 123
Object = 123
Object = String 1
Object = String 2
Object = String 3

You might be wondering what just happened. Well, let’s have a look at what methods of the NSMutableArray class we actually used:

addObject:

This method allows us to add an object to the end of a mutable array.

removeObject:

Using this method, we can remove a specific object from the array. Remember that we pass an object to this method, not an index of the object. To remove an object using an index into the array, we must use the removeObjectAtIndex: method.

addObjectsFromArray:

With this method, we can add objects from one array (either mutable or immutable) into our mutable array.

Warning

Bear in mind that during fast enumeration of a mutable array, you must not add to or remove anything from that array or you will get a runtime error. This is the default behavior of mutable arrays during fast enumeration. There are two ways of avoiding this. Either simply follow the rule of not modifying an array while fast enumerating it, or, if you prefer the more proactive approach, you can subclass NSMutableArray and change the behavior for yourself. This topic is outside the scope of this book and will not be discussed.

If you are interested in block objects (and we’ll see good reasons to be, later in the book, in Chapter 6), you can also enumerate objects in your arrays using the enumerateObjectsUsingBlock: method. The block object passed to this method should:

  • Return no value.

  • Have three parameters:

    • First parameter of type id, which will be the object being enumerated at each loop of enumeration.

    • Second parameter of type NSUInteger, which will tell you the index of the current object being enumerated.

    • Last but not least, a parameter of type *BOOL, which you can use to stop the enumeration. This is a pointer to a boolean variable, which should be NO as long as you want the enumeration to proceed. You can change the value of this pointer to YES in order to stop the enumeration at any time. You would use this if you are looking for an object in an array and you would like to stop the enumeration as soon as you’ve found that object, since there is no point continuing the enumeration if you’ve already found your object.

    NSArray *myArray = @[
    @"String 1",
    @"String 2",
    @"String 3",
    @"String 4"];
    
    [myArray enumerateObjectsUsingBlock:
    ^(__strong id obj, NSUInteger idx, BOOL *stop) {
     NSLog(@"Object = %@", obj);
    }];

If you need to sort an array, simply use the new block-based sorting methods of NSArray or NSMutableArray. Just remember that the sorting methods of NSArray return a new instance of NSArray and leave the original array intact, since NSArray cannot be modified (sorting can modify an array) after it has been allocated and initialized. This is in comparison to the sorting methods of NSMutableArray, where the original array will be the target of sorting and the sorting methods will not return a new array. Let’s look at sorting a mutable array:

NSMutableArray *myArray = [NSMutableArray arrayWithArray:@[
                         @"String 2",
                         @"String 4",
                         @"String 1",
                         @"String 3"]];

[myArray sortUsingComparator:
^NSComparisonResult(__strong id obj1, __strong id obj2) {

NSString *string1 = (NSString *)obj1;
NSString *string2 = (NSString *)obj2;
return [string1 compare:string2];

}];

NSLog(@"myArray = %@", myArray);

NSLog(@"%d", [@"String 3" compare:@"String 1"]);

The results will then be printed to the console, as follows:

myArray = (
    "String 1",
    "String 2",
    "String 3",
    "String 4"
)

So, what happened? We simply called the sortUsingComparator: method of our array. This method takes in a block object (marked by the initial ^ character) that has to return a value of type NSComparisonResult. This value can be any of the following:

NSOrderedSame

The two values being compared are equal.

NSOrderedAscending

The value on the left of the comparison is smaller than the value on the right. Think of it as this: transition from value 1 (left) to value 2 (right) is ascending, meaning that value 1 is smaller.

NSOrderedDescending

The value on the right is smaller than the value on the left. In other words, the transition from value 1 (left) to value 2 (right) is descending, meaning that value 1 is bigger than value 2.

So if we get String 3 as value 1 (left) and String 1 as value 2 (right), the sort function compares the two S characters and finds them the same, then the two t characters, and so on. Finally, when the sort function reaches the 3 and the 1, it finds that 1 is lower than 3 in the UTF-8 string character set, and therefore that the second element is lower than the first.

The block object submitted to the sortUsingComparator: method takes two parameters:

First object of type id

This is the first object in the comparison in each iteration.

Second object of type id

This is the second object in the comparison in each iteration.

So when sorting the array, simply use a block-based approach. It’s the way Apple is pushing developers to go forward with their implementations, so it’s good to know about block objects.

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