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iOS 5 Programming Cookbook

Cover of iOS 5 Programming Cookbook by Vandad Nahavandipoor Published by O'Reilly Media, Inc.
  1. iOS 5 Programming Cookbook
    1. SPECIAL OFFER: Upgrade this ebook with O’Reilly
    2. A Note Regarding Supplemental Files
    3. 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
    4. 1. The Basics
      1. 1.0. Introduction
      2. 1.1. Creating a Simple iOS App in Xcode
      3. 1.2. Understanding Interface Builder
      4. 1.3. Compiling iOS Apps
      5. 1.4. Running iOS Apps on the Simulator
      6. 1.5. Running iOS Apps on iOS Devices
      7. 1.6. Packaging iOS Apps for Distribution
      8. 1.7. Declaring Variables in Objective-C
      9. 1.8. Allocating and Making Use of Strings
      10. 1.9. Comparing Values in Objective-C with an If Statement
      11. 1.10. Implementing Loops with For Statements
      12. 1.11. Implementing While Loops
      13. 1.12. Creating Custom Classes
      14. 1.13. Defining Functionality for Classes
      15. 1.14. Defining Two or More Methods with the Same Name
      16. 1.15. Allocating and Initializing Objects
      17. 1.16. Adding Properties to Classes
      18. 1.17. Moving From Manual Reference Counting to Automatic Reference Counting
      19. 1.18. Typecasting with Automatic Reference Counting
      20. 1.19. Delegating Tasks with Protocols
      21. 1.20. Determining Whether Instance or Class Methods Are Available
      22. 1.21. Determining Whether a Class Is Available at Runtime
      23. 1.22. Allocating and Making Use of Numbers
      24. 1.23. Allocating and Making Use of Arrays
      25. 1.24. Allocating and Making Use of Dictionaries
      26. 1.25. Allocating and Making Use of Sets
      27. 1.26. Creating Bundles
      28. 1.27. Loading Data From the Main Bundle
      29. 1.28. Loading Data From Other Bundles
      30. 1.29. Sending Notifications with NSNotificationCenter
      31. 1.30. Listening for Notifications Sent From NSNotificationCenter
    5. 2. Implementing Controllers and Views
      1. 2.0. Introduction
      2. 2.1. Displaying Alerts with UIAlertView
      3. 2.2. Creating and Using Switches with UISwitch
      4. 2.3. Picking Values with UIPickerView
      5. 2.4. Picking the Date and Time with UIDatePicker
      6. 2.5. Implementing Range Pickers with UISlider
      7. 2.6. Grouping Compact Options with UISegmentedControl
      8. 2.7. Presenting and Managing Views with UIViewController
      9. 2.8. Implementing Navigation with UINavigationController
      10. 2.9. Manipulating a Navigation Controller’s Array of View Controllers
      11. 2.10. Displaying an Image on a Navigation Bar
      12. 2.11. Adding Buttons to Navigation Bars Using UIBarButtonItem
      13. 2.12. Presenting Multiple View Controllers with UITabBarController
      14. 2.13. Displaying Static Text with UILabel
      15. 2.14. Accepting User Text Input with UITextField
      16. 2.15. Displaying Long Lines of Text with UITextView
      17. 2.16. Adding Buttons to the User Interface with UIButton
      18. 2.17. Displaying Images with UIImageView
      19. 2.18. Creating Scrollable Content with UIScrollView
      20. 2.19. Loading Web Pages with UIWebView
      21. 2.20. Presenting Master-Detail Views with UISplitViewController
      22. 2.21. Enabling Paging with UIPageViewController
      23. 2.22. Displaying Popovers with UIPopoverController
      24. 2.23. Displaying Progress with UIProgressView
      25. 2.24. Listening and Reacting to Keyboard Notifications
    6. 3. Constructing and Using Table Views
      1. 3.0. Introduction
      2. 3.1. Instantiating a Table View
      3. 3.2. Assigning a Delegate to a Table View
      4. 3.3. Populating a Table View with Data
      5. 3.4. Receiving and Handling Table View Events
      6. 3.5. Using Different Types of Accessories in a Table View Cell
      7. 3.6. Creating Custom Table View Cell Accessories
      8. 3.7. Displaying Hierarchical Data in Table Views
      9. 3.8. Enabling Swipe Deletion of Table View Cells
      10. 3.9. Constructing Headers and Footers in Table Views
      11. 3.10. Displaying Context Menus on Table Views Cells
      12. 3.11. Moving Cells and Sections in Table Views
      13. 3.12. Deleting Cells and Sections From Table Views
    7. 4. Storyboards
      1. 4.0. Introduction
      2. 4.1. Creating a Project with Storyboards
      3. 4.2. Adding a Navigation Controller to a Storyboard
      4. 4.3. Passing Data From One Screen to Another
      5. 4.4. Adding a Storyboard to an Existing Project
    8. 5. Concurrency
      1. 5.0. Introduction
      2. 5.1. Constructing Block Objects
      3. 5.2. Accessing Variables in Block Objects
      4. 5.3. Invoking Block Objects
      5. 5.4. Dispatching Tasks to Grand Central Dispatch
      6. 5.5. Performing UI-Related Tasks with GCD
      7. 5.6. Performing Non-UI Related Tasks Synchronously with GCD
      8. 5.7. Performing Non-UI Related Tasks Asynchronously with GCD
      9. 5.8. Performing Tasks After a Delay with GCD
      10. 5.9. Performing a Task Only Once with GCD
      11. 5.10. Grouping Tasks Together with GCD
      12. 5.11. Constructing Your Own Dispatch Queues with GCD
      13. 5.12. Running Tasks Synchronously with Operations
      14. 5.13. Running Tasks Asynchronously with Operations
      15. 5.14. Creating Dependency Between Operations
      16. 5.15. Creating Timers
      17. 5.16. Creating Concurrency with Threads
      18. 5.17. Invoking Background Methods
      19. 5.18. Exiting Threads and Timers
    9. 6. Core Location and Maps
      1. 6.0. Introduction
      2. 6.1. Creating a Map View
      3. 6.2. Handling the Events of a Map View
      4. 6.3. Pinpointing the Location of a Device
      5. 6.4. Displaying Pins on a Map View
      6. 6.5. Displaying Pins with Different Colors on a Map View
      7. 6.6. Displaying Custom Pins on a Map View
      8. 6.7. Converting Meaningful Addresses to Longitude and Latitude
      9. 6.8. Converting Longitude and Latitude to a Meaningful Address
    10. 7. Implementing Gesture Recognizers
      1. 7.0. Introduction
      2. 7.1. Detecting Swipe Gestures
      3. 7.2. Detecting Rotation Gestures
      4. 7.3. Detecting Panning and Dragging Gestures
      5. 7.4. Detecting Long Press Gestures
      6. 7.5. Detecting Tap Gestures
      7. 7.6. Detecting Pinch Gestures
    11. 8. Networking, JSON, XML, and Twitter
      1. 8.0. Introduction
      2. 8.1. Downloading Asynchronously with NSURLConnection
      3. 8.2. Handling Timeouts in Asynchronous Connections
      4. 8.3. Downloading Synchronously with NSURLConnection
      5. 8.4. Modifying a URL Request with NSMutableURLRequest
      6. 8.5. Sending HTTP GET Requests with NSURLConnection
      7. 8.6. Sending HTTP POST Requests with NSURLConnection
      8. 8.7. Sending HTTP DELETE Requests with NSURLConnection
      9. 8.8. Sending HTTP PUT Requests with NSURLConnection
      10. 8.9. Serializing Arrays and Dictionaries into JSON
      11. 8.10. Deserializing JSON into Arrays and Dictionaries
      12. 8.11. Integrating Twitter Functionality into Your Apps
      13. 8.12. Parsing XML with NSXMLParser
    12. 9. Audio and Video
      1. 9.0. Introduction
      2. 9.1. Playing Audio Files
      3. 9.2. Handling Interruptions While Playing Audio
      4. 9.3. Recording Audio
      5. 9.4. Handling Interruptions While Recording Audio
      6. 9.5. Playing Audio Over Other Active Sounds
      7. 9.6. Playing Video Files
      8. 9.7. Capturing Thumbnails From a Video File
      9. 9.8. Accessing the Music Library
    13. 10. Address Book
      1. 10.0. Introduction
      2. 10.1. Retrieving a Reference to an Address Book
      3. 10.2. Retrieving All the People in the Address Book
      4. 10.3. Retrieving Properties of Address Book Entries
      5. 10.4. Inserting a Person Entry into the Address Book
      6. 10.5. Inserting a Group Entry into the Address Book
      7. 10.6. Adding Persons to Groups
      8. 10.7. Searching the Address Book
      9. 10.8. Retrieving and Setting a Person’s Address Book Image
    14. 11. Camera and the Photo Library
      1. 11.0. Introduction
      2. 11.1. Detecting and Probing the Camera
      3. 11.2. Taking Photos with the Camera
      4. 11.3. Taking Videos with the Camera
      5. 11.4. Storing Photos in the Photo Library
      6. 11.5. Storing Videos in the Photo Library
      7. 11.6. Retrieving Photos and Videos From the Photo Library
      8. 11.7. Retrieving Assets From the Assets Library
      9. 11.8. Editing Videos on an iOS Device
    15. 12. Multitasking
      1. 12.0. Introduction
      2. 12.1. Detecting the Availability of Multitasking
      3. 12.2. Completing a Long-Running Task in the Background
      4. 12.3. Receiving Local Notifications in the Background
      5. 12.4. Playing Audio in the Background
      6. 12.5. Handling Location Changes in the Background
      7. 12.6. Saving and Loading the State of Multitasking iOS Apps
      8. 12.7. Handling Network Connections in the Background
      9. 12.8. Handling Notifications Delivered to a Waking App
      10. 12.9. Responding to Changes in App Settings
      11. 12.10. Opting Out of Multitasking
    16. 13. Core Data
      1. 13.0. Introduction
      2. 13.1. Creating a Core Data Model with Xcode
      3. 13.2. Generating Class Files for Core Data Entities
      4. 13.3. Creating and Saving Data Using Core Data
      5. 13.4. Reading Data From Core Data
      6. 13.5. Deleting Data From Core Data
      7. 13.6. Sorting Data in Core Data
      8. 13.7. Boosting Data Access in Table Views
      9. 13.8. Implementing Relationships in Core Data
    17. 14. Dates, Calendars, and Events
      1. 14.0. Introduction
      2. 14.1. Retrieving the List of Calendars
      3. 14.2. Adding Events to Calendars
      4. 14.3. Accessing the Contents of Calendars
      5. 14.4. Removing Events From Calendars
      6. 14.5. Adding Recurring Events to Calendars
      7. 14.6. Retrieving the Attendees of an Event
      8. 14.7. Adding Alarms to Calendars
      9. 14.8. Handling Event Changed Notifications
      10. 14.9. Presenting Event View Controllers
      11. 14.10. Presenting Event Edit View Controllers
    18. 15. Graphics and Animations
      1. 15.0. Introduction
      2. 15.1. Enumerating and Loading Fonts
      3. 15.2. Drawing Text
      4. 15.3. Constructing, Setting, and Using Colors
      5. 15.4. Drawing Images
      6. 15.5. Drawing Lines
      7. 15.6. Constructing Paths
      8. 15.7. Drawing Rectangles
      9. 15.8. Adding Shadows to Shapes
      10. 15.9. Drawing Gradients
      11. 15.10. Displacing Shapes Drawn on Graphic Contexts
      12. 15.11. Scaling Shapes Drawn on Graphic Contexts
      13. 15.12. Rotating Shapes Drawn on Graphic Contexts
      14. 15.13. Animating and Moving Views
      15. 15.14. Animating and Scaling Views
      16. 15.15. Animating and Rotating Views
    19. 16. Core Motion
      1. 16.0. Introduction
      2. 16.1. Detecting the Availability of an Accelerometer
      3. 16.2. Detecting the Availability of a Gyroscope
      4. 16.3. Retrieving Accelerometer Data
      5. 16.4. Detecting Shakes on an iOS Device
      6. 16.5. Retrieving Gyroscope Data
    20. 17. iCloud
      1. 17.0. Introduction
      2. 17.1. Setting Up Your App for iCloud
      3. 17.2. Storing and Synchronizing Dictionaries in iCloud
      4. 17.3. Creating and Managing Folders for Apps in iCloud
      5. 17.4. Searching for Files and Folders in iCloud
      6. 17.5. Storing User Documents in iCloud
      7. 17.6. Managing the State of Documents in iCloud
      8. 17.7. Handling Conflicts in iCloud Documents
    21. Index
    22. About the Author
    23. Colophon
    24. SPECIAL OFFER: Upgrade this ebook with O’Reilly
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1.27. Loading Data From the Main Bundle

Problem

You have added a resource (such as an image) to your Xcode project and now, at runtime, you would like to access that resource.

Solution

Use the mainBundle class method of the NSBundle class in order to retrieve your main bundle. Once that is done, use the pathForResource:ofType: method of your main bundle to retrieve the path for that specific resource. Once the path is detected, depending on the type of resource, you can either pass the path to your file to a class such as UIImage or NSData, or you can manually access the file using NSFileManager.

Note

It is required that you give a unique name to each resource inside your main bundle. For instance, it is not good practice to have a file named Default.png in more than one place inside your main bundle. Different ways of loading a resource from a bundle could then yield different results. As a result, make sure you give unique names to your files inside any bundle, regardless of whether it is the main bundle or a custom bundle that you’ve created (see Recipe 1.26).

Discussion

To access the main bundle, we can use the mainBundle class method of the NSBundle class. Bundles are all of type NSBundle and once you have an instance of a bundle, you can load resources from that bundle.

Note

Every app’s main bundle has a flat hierarchy on disk when it is compiled for submission to App Store. That means all the files that get wrapped up in your app bundle will be placed on the root folder of the main bundle. In other words, the main bundle has only one folder, the root folder, and all files and resources are stored in that folder. Even if you have a folder on disk with a few files in it and drag and drop it into Xcode, only the files in that folder will be placed in the main bundle’s file hierarchy, not the folder itself.

For instance, let’s say that you have an image called AlanSugar.png sitting on your desktop. Simply drag and drop it into Xcode. At this point, Xcode will display a dialog to you, asking you which project this file has to be added to and whether you want this file to be copied over to the project’s folder, if need be. This dialog will look similar to that shown in Figure 1-34.

Xcode asking which project a file has to be added to

Figure 1-34. Xcode asking which project a file has to be added to

In this dialog, make sure that the “Copy items into destination group’s folder (if needed)” item is selected. This will copy the file that you drop into Xcode to the target app’s folder. Now, if you delete the file on your desktop, it won’t get deleted from your project because your project has its own copy. It’s generally good practice to do this unless for specific reasons you decide not to (and I’ve experienced many of these reasons myself). After you drag and drop the file, the file AlanSugar.png is in the project’s main bundle and you can retrieve its path in this way:

- (BOOL)            application:(UIApplication *)application
  didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{

  NSString *alanSugarFilePath =
  [[NSBundle mainBundle] pathForResource:@"AlanSugar"
                                  ofType:@"png"];

  if ([alanSugarFilePath length] > 0){
    UIImage *image = [UIImage imageWithContentsOfFile:alanSugarFilePath];
    if (image != nil){
      NSLog(@"Successfully loaded the file as an image.");
    } else {
      NSLog(@"Failed to load the file as an image.");
    }

  } else {
    NSLog(@"Could not find this file in the main bundle.");
  }

  self.window = [[UIWindow alloc] initWithFrame:
                 [[UIScreen mainScreen] bounds]];

  self.window.backgroundColor = [UIColor whiteColor];
  [self.window makeKeyAndVisible];
  return YES;
}

The output of the pathForResource:ofType: method of NSBundle will be either a valid path or nil if the specified resource cannot be found in the target bundle. So after you call this method, it is best to check whether the path could actually be retrieved. If so, the code shown passes the path of the file to the UIImage class in order to load the AlanSugar.png file into memory as an image.

Similarly, if you wanted to load the data of that file into memory, instead of retrieving this image as an image object, you could use the NSData class:

- (BOOL)          application:(UIApplication *)application
didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{

  NSString *alanSugarFilePath =
  [[NSBundle mainBundle] pathForResource:@"AlanSugar"
                                  ofType:@"png"];

  if ([alanSugarFilePath length] > 0){

    NSError *readError = nil;

    NSData *dataForFile =
    [[NSData alloc] initWithContentsOfFile:alanSugarFilePath
                                   options:NSMappedRead
                                     error:&readError];

    if (readError == nil &&
        dataForFile != nil){
      NSLog(@"Successfully loaded the data.");
    } else if (readError == nil &&
               dataForFile == nil){
      NSLog(@"No data could be loaded.");
    } else {
      NSLog(@"An error occured while loading data. Error = %@", readError);
    }

  } else {
    NSLog(@"Could not find this file in the main bundle.");
  }

  self.window = [[UIWindow alloc] initWithFrame:
                 [[UIScreen mainScreen] bounds]];

  self.window.backgroundColor = [UIColor whiteColor];
  [self.window makeKeyAndVisible];
  return YES;
}

See Also

Recipe 1.26

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