AppDelegate.m

/*
     File: AppDelegate.m
 Abstract: The application delegate class used for adding our navigation controller.
  Version: 1.3
 
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 */
 
#import "AppDelegate.h"
#import "Level1ViewController.h"
 
NSString *kItemTitleKey     = @"itemTitle";     // dictionary key for obtaining the item's title to display in each cell
NSString *kChildrenKey      = @"itemChildren";  // dictionary key for obtaining the item's children
NSString *kCellIdentifier   = @"MyIdentifier";  // the table view's cell identifier
 
NSString *kRestoreLocationKey = @"RestoreLocation"; // preference key to obtain our restore location
 
 
@implementation AppDelegate
 
@synthesize window, outlineData, navigationController, savedLocation;
 
- (id)init
{
    self = [super init];
    if (self)
    {
        // load the drill-down list content from the plist filem
        // this plist contains the outline mapping each level of the list hierarchy
        //
        NSString *path = [[NSBundle mainBundle] bundlePath];
        NSString *finalPath = [path stringByAppendingPathComponent:@"outline.plist"];
        outlineData = [[NSDictionary dictionaryWithContentsOfFile:finalPath] retain];
    }
    return self;
}
 
- (void)dealloc
{
    [navigationController release];  
    [window release];
    [outlineData release];
    [savedLocation release];
    
    [super dealloc];
}
 
- (void)applicationDidFinishLaunching:(UIApplication *)application
{
    // fetch the top level items in our outline (level 1)
    NSArray *topLevel1Content = [outlineData objectForKey:kChildrenKey];
    
    // give the top view controller its content
    ((Level1ViewController*)navigationController.topViewController).listContent = topLevel1Content;
        
    // load the stored preference of the user's last location from a previous launch
    NSMutableArray *tempMutableCopy = [[[NSUserDefaults standardUserDefaults] objectForKey:kRestoreLocationKey] mutableCopy];
    self.savedLocation = tempMutableCopy;
    [tempMutableCopy release];
    if (savedLocation == nil)
    {
        // user has not launched this app nor navigated to a particular level yet, start at level 1, with no selection
        savedLocation = [[NSMutableArray arrayWithObjects:
                          [NSNumber numberWithInteger:-1],  // item selection at 1st level (-1 = no selection)
                          [NSNumber numberWithInteger:-1],  // .. 2nd level
                          [NSNumber numberWithInteger:-1],  // .. 3rd level
                          nil] retain];
    }
    else
    {
        NSInteger selection = [[savedLocation objectAtIndex:0] integerValue];   // read the saved selection at level 1
        if (selection != -1)
        {
            // user was last at level 2 or deeper
            //
            // note: this starts a chain reaction down each level (2nd, 3rd, etc.)
            // so that each level restores itself and pushes further down until there's no further stored selections.
            //
            [(Level1ViewController*)navigationController.topViewController restoreLevel:topLevel1Content withSelectionArray:savedLocation];
        }
        else
        {
            // no saved selection, so user was at level 1 the last time
        }
    }
    
    // add the navigation controller's view to the window
    [window addSubview:[navigationController view]];
    [window makeKeyAndVisible];
    
    // register our preference selection data to be archived
    NSDictionary *savedLocationDict = [NSDictionary dictionaryWithObject:savedLocation forKey:kRestoreLocationKey];
    [[NSUserDefaults standardUserDefaults] registerDefaults:savedLocationDict];
    [[NSUserDefaults standardUserDefaults] synchronize];
}
 
@end