When using a NSURLRequest object to access a server, the delegate methods of NSURLConnection offer a means to be notified when an authentication challenge has been requested.

This post will show one approach for managing URL requests that require authentication.

Initiate the URL Request

/*---------------------------------------------------------------------------
* Begin the authentication process 
*--------------------------------------------------------------------------*/
- (void)startAuthentication
{
  NSURL *url = [NSURL URLWithString:@"http://protectedURL.com"];
  NSMutableURLRequest *urlRequest = [NSMutableURLRequest requestWithURL:url];
 
  // Start the connection request
  // Assumes NSURLConnection *urlConnection is defined as an
  // instance variable
   urlConnection = [[NSURLConnection alloc] initWithRequest:urlRequest delegate:self];
}

Answer Authentication Challenge

If an authentication challenge is returned from the URL request, the method below will be called. To respond to the challange, create a NSURLCredential object, setting the username and password.

Notice that we can check to see how many times the challenge/response has failed and present an error message as needed.

/*---------------------------------------------------------------------------
* Received a server challenge
*--------------------------------------------------------------------------*/
- (void)connection:(NSURLConnection *)connection 
      didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge
{
  // Access has failed two times...
  if ([challenge previousFailureCount] > 1)
  {
    [urlConnection release];
 
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Authentication Error"
                                     message:"Too many unsuccessul login attempts." 
                                     delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
 
    [alert show];
    [alert release];
  }
  else 
  {
    // Answer the challenge
    NSURLCredential *cred = [[[NSURLCredential alloc] initWithUser:@"admin" password:@"password"
       persistence:NSURLCredentialPersistenceForSession] autorelease];
    [[challenge sender] useCredential:cred forAuthenticationChallenge:challenge];
  }
}
 
/*---------------------------------------------------------------------------
* Finished loading URL
*--------------------------------------------------------------------------*/
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
  NSLog(@"Connection success.");  
 
  [urlConnection release];
}
 
/*---------------------------------------------------------------------------
* URL connection fail
*--------------------------------------------------------------------------*/
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
  NSLog(@"Connection failure.");
 
  [urlConnection release];
}

Heads Up Display – MBProgressHUD

The inaugural iOS open source project is MBProgressHUD, you can find source code here on git: MBProgressHUD

For those unfamiliar with HUD, it refers to Heads Up Display, a view that is overlayed on another view, typically to show an activity indicator and/or offer a means to interact with the UI. A good example of an HUD is when playing a movie with the built in movie player. When you tap the screen, the movie player will show a series of controls on the display. Another common example, and one that is pertinent to MBProgressHUD, is showing progress indicators on top of an existing view. For example, when accessing a remote service, to provide feedback to the user you may opt to display a “Please Wait” message.

MBProgressHUD offers a number of interesting options from a simple activity indicator to a mode switching display that can show multiple messages, in sequence. See the figures below for a few examples:

MBProgressHUD includes a demo project that you compile and run in the simulator to get a feel for how things work.

Open Source Code / Project Recommendations ?

If you have written, worked with or otherwise know of an interesting open source project, one that is focused on iOS or Cocoa, feel free to send me a note. Even a simple class/category that is open source is welcome – for example MBProgressHUD is only two files, an interface (.h) and implementation (.m) . You can reach me at here.

Licensing and Caveats

Regarding all open source projects, please review any license agreement that is included with the project for more information about permissions, limitations and warranties.

As you would expect, iPhone Developer Tips offers no warranties of any kind regarding open source projects, use at your own risk.

I had a few strings defined as constants and I was interested to see if there was a painless way to store the values as obfuscated strings, and when running the application, un-obfuscate the strings and use the same within the application.

Using Exclusive-Or (XOR) to Obfuscate an NSString

The basic concept is that for each character in a string, I XOR the value against a key value, replacing the original character with the new XOR’d character. This will create a string that is unrecognizable from the original. To get the original string back, perform the same XOR operation with the same key. The obfuscate method is shown below.

- (NSString *)obfuscate:(NSString *)string withKey:(NSString *)key
{
  // Create data object from the string
  NSData *data = [string dataUsingEncoding:NSUTF8StringEncoding];
 
  // Get pointer to data to obfuscate
  char *dataPtr = (char *) [data bytes];
 
  // Get pointer to key data
  char *keyData = (char *) [[key dataUsingEncoding:NSUTF8StringEncoding] bytes];
 
  // Points to each char in sequence in the key
  char *keyPtr = keyData;
  int keyIndex = 0;
 
  // For each character in data, xor with current value in key
  for (int x = 0; x < [data length]; x++) 
  {
    // Replace current character in data with 
    // current character xor'd with current key value.
    // Bump each pointer to the next character
    *dataPtr = *dataPtr++ ^ *keyPtr++; 
 
    // If at end of key data, reset count and 
    // set key pointer back to start of key value
    if (++keyIndex == [key length])
      keyIndex = 0, keyPtr = keyData;
  }
 
  return [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease];
}

Test Obfuscation

Pass in the string to obfuscate as well as a key which will provide the characters to use in the XOR process. To un-obfuscate a string, call the method with the obfuscated string and the same key.

Below is a short test of the obfuscation:

NSString *str = @"iPhoneDeveloperTips"; 
NSLog(@"Input string:%@", str);		
 
// Obfuscate string
NSString *obfuscatedStr = [self obfuscate:str withKey:@"+@$"];
NSLog(@"Obfuscated string:%@", obfuscatedStr);	
 
// Run obfuscate again to get the original string
str = [self obfuscate:obfuscatedStr withKey:@"+@$"];
NSLog(@"Final string:%@", str);

The output will look as follows:

Note: The resulting obfuscated string may include non-printable characters, so if you print to the console as shown above, don’t be surprised if the output contains what looks to be spaces or newline characters.

Caveat

For any number of reasons, including the key is stored as part of the application, this approach is by no means a substitution for real encryption. If you have sensitive data you need to protect, use the Keychain services. With that said, there are times when storing a string in a format other than clear text in your application may be of interest.

As with all previous Voices That Matters iPhone events, you will have an opportunity to learn from industry leaders who literally “Wrote the Books” on iOS Development. This two-day conference features a wide range of sessions, including:

* Multitasking
* Game design
* Accessibility
* Designing a killer user interface
* Augmented reality
* Unit testing
* Internationalization
* Many other timely and compelling discussions

Lead by industry experts and authors, this is a weekend packed with sessions and interactive discussions,

Enjoy a unique venue that offers an opportunity to network with other developers and mingle with experts including Mike Lee, Aaron Hillegass, Erica Sadun, Stephen Kochan, Rod Strougo, and Christian Hofstader, to name a few.

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iPhone-Simulator Cropper

This tool works by capturing the screen of the simulator runnning on your system. One really slick feature is the option to create captured images in two primary formats – first, a format suitable for upload to iTunes for your application screenshots – second, capturing a screenshot that is suitable for display on a website.

The following images show the iPhone-Simulator Cropper application, as well as two sample images captured:

iTunes Connect / App Store:

Website (iPhone Device from Apple Marketing):

However, they are times when having a method to truncate a string without using a UI control would be handy. In this post I’ll create a category which will add a method to the NSString class to do just that. You can read more about working with categories in this post: Introduction to Categories.

NSString Category

Start by creating a new interface file with the name: NSString+TruncateToWidth.h – appending the method name to the class is a common naming convention when working with categories.

The code below defines a method that will be available to all NSString objects. The method will truncate a string to a specific width, using the font size to properly determine the string size before truncating:

@interface NSString (TruncateToWidth)
 
- (NSString*)stringByTruncatingToWidth:(CGFloat)width withFont:(UIFont *)font;
 
@end

Code to Truncate NSString

The implementation of the stringByTruncatingToWidth method follows, add this code to the NSString+TruncateToWidth.m file.

#import "NSString+TruncateToWidth.h"
 
#define ellipsis @"…"
 
@implementation NSString (TruncateToWidth)
 
- (NSString*)stringByTruncatingToWidth:(CGFloat)width withFont:(UIFont *)font
{
  // Create copy that will be the returned result
  NSMutableString *truncatedString = [[self mutableCopy] autorelease];
 
  // Make sure string is longer than requested width
  if ([self sizeWithFont:font].width > width)
  {
    // Accommodate for ellipsis we'll tack on the end
    width -= [ellipsis sizeWithFont:font].width;
 
    // Get range for last character in string
    NSRange range = {truncatedString.length - 1, 1};
 
    // Loop, deleting characters until string fits within width
    while ([truncatedString sizeWithFont:font].width > width) 
    {
      // Delete character at end
      [truncatedString deleteCharactersInRange:range];
 
      // Move back another character
      range.location--;
    }
 
    // Append ellipsis
    [truncatedString replaceCharactersInRange:range withString:ellipsis];
  }
 
  return truncatedString;
}
 
@end

Notice that the desired final width of the string is passed in, as well as the font that will be used when calculating the size (width) of the string. The process is quite simple: change the incoming width to accommodate an ellipsis on the end of the string – loop through the string removing characters from the end until the desired width is reached – append an ellipsis onto the string.

Calling the Truncate NSString Method

You can now call the method stringByTruncatingToWidth:withFont: on any NSString object:

NSString *str = @"Lorem ipsum dolor sit amet, consectetuer adipiscing";
 
// Adjust the width parameter to change the final string width
str = [str stringByTruncatingToWidth:170 withFont:[UIFont systemFontOfSize:15]];
NSLog(@"%@", str);

The output from above would look as follows:

Lorem ipsum dolor sit…

You can download older versions of Xcode by logging into Apple Developer Connection – Downloads and ADC Program Assests (http://connect.apple.com) – You will need to be a member of the developer program to login.

Once on the site, from the Downloads section, choose Developer Tools – you will be shown with a list of all Xcode versions, back to 1.0 released in October of 2004.

Install Multiple Versions of Xcode

To keep from overwriting an existing installation, you can specify the path for Xcode during the install process. For example, the default location is /Developer, to install an older version you could instruct Xcode to install into a simliar name such as /Developer-3.1

To change the install path, click on the Location header in the install dialog:

Choose a new path for the Essentials Package:

For both posts, in order to create a working example that one could download and run as is, the code examples referenced a movie that I included in the application bundle. Although handy, this prompted a number of questions about how to play a movie from a remote resource.

I’ve updated the original examples for both posts, with an option to play movies from the application bundle or from a remote server.

Play Movie from Server

The first change I made was in CustomMoviePlayerViewController.m, where I added a method to initialize the movie player with a NSURL object:

- (id)initWithURL:(NSURL *)URL
{
  if (self = [super init])
  {
    movieURL = URL;
    [movieURL retain];
 
  }
  return self;
}
 
- (id)initWithPath:(NSString *)moviePath
{
  if (self = [super init])
  {
    movieURL = [NSURL fileURLWithPath:moviePath];    
    [movieURL retain];
  }
  return self;
}

For both methods, the end result is an initialized NSURL object.

The other code change is in TestViewController.m where I updated the loadMoviePlayer method to support calling either of the above methods:

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- (void)loadMoviePlayer
{  
/*
  // Play movie from app bundle
  NSString *path = [[NSBundle mainBundle] pathForResource:@"Movie-1" ofType:@"mp4" inDirectory:nil];
  moviePlayer = [[[CustomMoviePlayerViewController alloc] initWithPath:path] autorelease];
*/
 
  // Play movie from URL
  NSURL *movieURL = [NSURL URLWithString:@"http://someurlsomewhere.com/movie.mp4"];
  moviePlayer = [[[CustomMoviePlayerViewController alloc] initWithURL:movieURL] autorelease];
 
  // Show the movie player as modal
  [self presentModalViewController:moviePlayer animated:YES];
 
  // Prep and play the movie
  [moviePlayer readyPlayer];    
}

Comment in/out the relevant code in lines 4 – 11 to swap between playing from a file in the bundle and a movie accessible on a remote server.

Download Movie Player Source Code

MoviePlayer in Landscape Mode

MoviePlayer in Portrait Mode (requires 3.2 OS and greater)

In this post I want to show you a few minor changes you can make to the previous app to display a movie in portrait mode, something that was not possible in earlier (pre 3.2) OS versions. With that said, back in January of 2010 I did cover a means to create the illusion that a movie was in portrait mode, if this piques your interest, have a look here: Play iPhone Movies in Portrait Mode with MPMoviePlayerController using Public API’s

The figure below shows the same movie as played back in landscape and portrait:

Play Movies in Portrait Mode

The code below is from the previous post and shows how to configure the movie player view to display in landscape:

MPMoviePlayerController *mp =  [[MPMoviePlayerController alloc]
     initWithContentURL:movieURL];
 
...
 
- (void) moviePlayerLoadStateChanged:(NSNotification*)notification 
{
  ...
  // Rotate the view for landscape playback
  [[self view] setBounds:CGRectMake(0, 0, 480, 320)];
  [[self view] setCenter:CGPointMake(160, 240)];
  [[self view] setTransform:CGAffineTransformMakeRotation(M_PI / 2)]; 
 
  // Set frame of movieplayer
  [[mp view] setFrame:CGRectMake(0, 0, 480, 320)];
 
  ...
}

To playback a movie in portrait mode is as easy as removing the code for the rotation and changing the frame of the movieplayer. I’ve also added a call to scale the movie so it fills the screen, this will maintain the aspect ratio.

- (void) moviePlayerLoadStateChanged:(NSNotification*)notification 
{
  ...
  // Rotate the view for landscape playback
  //	  [[self view] setBounds:CGRectMake(0, 0, 480, 320)];
  //		[[self view] setCenter:CGPointMake(160, 240)];
  //		[[self view] setTransform:CGAffineTransformMakeRotation(M_PI / 2)]; 
 
  // Set frame of movieplayer
  // [[mp view] setFrame:CGRectMake(0, 0, 480, 320)];
  [[mp view] setFrame:CGRectMake(0, 160, 320, 160)];
 
  // Scale uniformly, maintaining aspect ratio
  [mp setScalingMode:MPMovieScalingModeAspectFill];
 
  ...
}

This approach works on 3.2 (iPad) as well as 4.0 and greater. Needless to say, given the large display on the iPad this is a nice alternative as the user can watch videos without rotating the device.

Source Code

Download the source code to build an iPhone app that displays movies in portrait mode.

In the next post, Display iPhone Movies in Portrait Mode, I’ll show how to create a movie player that runs in a view that is not fullscreen as well as how to show a few lines of code to display a movie in portrait mode – the one caveat here is that both of the tips in the second post will apply only to OS versions 3.2 and up.

What’s Changed with MPMoviePlayerController in 3.2 and 4.0?

There are any number of changes in the MPMoviePlayerController, however, a few standout as potential roadblocks to getting a movie to display:

- In 3.1 and earlier versions, MPMoviePlayerController was full-screen only. Playing a movie was straight-forward, create a player, initialize with a file (path or URL) and call a method to start playback – the rest was taken care of for you.

- With 3.2 and later, movies can playback in fullscreen or a custom view, as well as portrait or landscape.

- The notification MPMoviePlayerContentPreloadDidFinishNotification has been deprecated. This notification was used in earlier versions to notify observers that a movie was loaded and ready to play.

The Movie Application

The application in this post is quite simple, it consists of a view controller with nothing more than a button to start playback and a second view controller to manage a MPMoviePlayerController and the NSURL of the movie. The two views are shown in the figures below:

Primary View Controller

The interface definition for the primary view is shown below:

#import <UIKit/UIKit.h>
 
@class CustomMoviePlayerViewController;
 
@interface TestViewController : UIViewController
{
  CustomMoviePlayerViewController  *moviePlayer;
  UIButton  *playButton;
}
 
@end

CustomMoviePlayerViewController is the controller for managing the movie, we’ll look at that code in a moment.

In the code below we create the view, add a play button, create a method for processing a button press event and within loadMoviePlayer, we get a reference to the movie file and create an instance of the CustomMoviePlayerViewController, which will load and play the movie.

- (void)loadView
{
  // Setup the view
  [self setView:[[[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]] autorelease]];
  [[self view] setBackgroundColor:[UIColor grayColor]];
  [[self view] setUserInteractionEnabled:YES];
 
  // Add play button 
  playButton = [[UIButton alloc] initWithFrame:CGRectMake(53, 212, 214, 36)];    
  [playButton setBackgroundImage:[UIImage imageNamed:@"playButton.png"] forState:UIControlStateNormal];
  [playButton addTarget:self action:@selector(buttonPressed:) forControlEvents: UIControlEventTouchUpInside];    
  [[self view] addSubview:playButton];  
}
 
- (void)buttonPressed:(UIButton *)button
{
  // If pressed, play movie
  if (button == playButton)
    [self loadMoviePlayer];	
}
 
- (void)loadMoviePlayer
{  
  // Play movie from the bundle
  NSString *path = [[NSBundle mainBundle] pathForResource:@"Movie-1" ofType:@"mp4" inDirectory:nil];
 
  // Create custom movie player   
  moviePlayer = [[[CustomMoviePlayerViewController alloc] initWithPath:path] autorelease];
 
  // Show the movie player as modal
  [self presentModalViewController:moviePlayer animated:YES];
 
  // Prep and play the movie
  [moviePlayer readyPlayer];    
}

Notice that the movie for this example is loaded from the application bundle. Also, once the custom movie player is created, the view is shown as a modal view.

Custom Movie Player View Controller

The interface definition for the movie view controller is below:

@interface CustomMoviePlayerViewController : UIViewController 
{
  MPMoviePlayerController *mp;
  NSURL  *movieURL;
}
 
- (id)initWithPath:(NSString *)moviePath;
- (void)readyPlayer;
 
@end

The initialization code is where the movie player and associated URL are created. The primary goal of the initialization is to create the NSURL needed by the movie player.

- (id)initWithPath:(NSString *)moviePath
{
  // Initialize and create movie URL
  if (self = [super init])
  {
    movieURL = [NSURL fileURLWithPath:moviePath];    
    [movieURL retain];
  }
  return self;
}

The code to create the player and setup the notifications is where we start to deal with the differences in how the movie player works on various OS versions. Notice below the call to respondsToSelector, this is the Apple recommended way to check for feature availability, versus looking for a specific OS version.

For devices running 3.2 and above, the movie player controller has a method named loadstate, if this exists we can access a few additional methods to set the player to fullscreen as well as request the movie to begin preloading.

Equally important is the distinction of which notification to setup – see lines 16 and 24.

You can read more about managing different OS version in this post Developing iPhone Apps with iOS4 SDK, Deploying to 3.x Devices

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- (void) readyPlayer
{
   mp =  [[MPMoviePlayerController alloc] initWithContentURL:movieURL];
 
  // For 3.2 devices and above
  if ([mp respondsToSelector:@selector(loadState)]) 
  {
    // Set movie player layout
    [mp setControlStyle:MPMovieControlStyleFullscreen];
    [mp setFullscreen:YES];
 
    // May help to reduce latency
    [mp prepareToPlay];
 
    // Register that the load state changed (movie is ready)
    [[NSNotificationCenter defaultCenter] addObserver:self 
        selector:@selector(moviePlayerLoadStateChanged:) 
        name:MPMoviePlayerLoadStateDidChangeNotification 
        object:nil];
  }  
  else
  {
    // Register to receive a notification when the movie is in memory and ready to play.
    [[NSNotificationCenter defaultCenter] addObserver:self 
        selector:@selector(moviePreloadDidFinish:) 
        name:MPMoviePlayerContentPreloadDidFinishNotification 
        object:nil];
  }
 
  // Register to receive a notification when the movie has finished playing. 
  [[NSNotificationCenter defaultCenter] addObserver:self 
        selector:@selector(moviePlayBackDidFinish:) 
        name:MPMoviePlayerPlaybackDidFinishNotification 
        object:nil];
}

The next two chunks of code are for each of the selectors, one for each notification. The code below is for earlier OS versions – nothing more than removing the notification and asking the movie to play.

/*---------------------------------------------------------------------------
* For 3.1.x devices
* For 3.2 and 4.x see moviePlayerLoadStateChanged: 
*--------------------------------------------------------------------------*/
- (void) moviePreloadDidFinish:(NSNotification*)notification 
{
  // Remove observer
  [[NSNotificationCenter 	defaultCenter] 
    removeObserver:self
    name:MPMoviePlayerContentPreloadDidFinishNotification
    object:nil];
 
  // Play the movie
   [mp play];
}

For the notification generated in 3.2 and above, there are a few more details to tend to:

/*---------------------------------------------------------------------------
* For 3.2 and 4.x devices
* For 3.1.x devices see moviePreloadDidFinish:
*--------------------------------------------------------------------------*/
- (void) moviePlayerLoadStateChanged:(NSNotification*)notification 
{
  // Unless state is unknown, start playback
  if ([mp loadState] != MPMovieLoadStateUnknown)
  {
    // Remove observer
    [[NSNotificationCenter defaultCenter] 
      removeObserver:self
      name:MPMoviePlayerLoadStateDidChangeNotification 
      object:nil];
 
    // When tapping movie, status bar will appear, it shows up
    // in portrait mode by default. Set orientation to landscape
    [[UIApplication sharedApplication] setStatusBarOrientation:UIInterfaceOrientationLandscapeRight animated:NO];
 
    // Rotate the view for landscape playback
    [[self view] setBounds:CGRectMake(0, 0, 480, 320)];
    [[self view] setCenter:CGPointMake(160, 240)];
    [[self view] setTransform:CGAffineTransformMakeRotation(M_PI / 2)]; 
 
    // Set frame of movie player
    [[mp view] setFrame:CGRectMake(0, 0, 480, 320)];
 
    // Add movie player as subview
    [[self view] addSubview:[mp view]];   
 
    // Play the movie
    [mp play];
  }
}

Beyond removing the notification, we also adjust the status bar, rotate the view, set the frame of the movie player, add the movie player as a subview in the view controller and wrap it all up by asking the movie to play.

Note: MPMoviePlayerViewController is also an option over creating your own view controller as I’ve done here.

Source Code

The easiest way to see all this working is to download the source code and step through the code in the debugger.