DockTilePlugIn/DockTilePlugIn.m

/*
     File: DockTilePlugIn.m
 Abstract: DockTile is a "game" which demonstrates the use of NSDockTile, and more importantly, the NSDockTilePlugIn protocol introduced in 10.6.
 
 The game is terribly simple: Your score goes up by 1 just by launching the app! So keep on launching the app over and over to reach new high scores.
 
 This class, DockTilePlugIn, is part of the dock plug-in for the app, which allows the dock tile to show the score even when the app is not running. This class implements the NSDockTilePlugIn protocol, which has just one required method, -setDockTile:.
 
 When the plug-in is loaded, an instance of DockTilePlugIn is instantiated, and setDockTile: called with an instance of NSDockTile.  The implementation of setDockTile: in DockTilePlugIn sets the plug-in as an observer of high score changes (using NSDistributedNotification), causing the badge on the dock tile to update everytime the score is updated. 
 
 The NSDistributedNotificationCenter registry happens with the 10.6 method addObserverForName:object:queue:block:. The body of the block has no references to the DockTilePlugIn instance, which means the notification does not cause it to be retained. In this case that does not matter (since setDockTile:nil is called, which removes the observer), but in some cases this is important to watch for.
  Version: 1.1
 
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*/
 
#import "DockTilePlugIn.h"
 
@implementation DockTilePlugIn
 
@synthesize highScoreObserver;
 
/* To update the score, we first make sure we are looking at the latest state of the defaults database, then we fetch the score and set it as the badge label.
*/
static void updateScore(NSDockTile *tile) {
    CFPreferencesAppSynchronize(CFSTR("com.apple.examples.DockTileApp"));
    NSInteger highScore = CFPreferencesGetAppIntegerValue(CFSTR("HighScore"), CFSTR("com.apple.examples.DockTileApp"), NULL);
    [tile setBadgeLabel:[NSString stringWithFormat:@"%ld", (long)highScore]];
}
 
- (void)setDockTile:(NSDockTile *)dockTile {
    if (dockTile) {
        // Attach an observer that will update the high score in the dock tile whenever it changes
    self.highScoreObserver = [[NSDistributedNotificationCenter defaultCenter] addObserverForName:@"com.apple.DockTileDemoHighScoreChanged" object:nil queue:nil usingBlock:^(NSNotification *notification) {
        updateScore(dockTile);  // Note that this block captures (and retains) dockTile for use later. Also note that it does not capture self, which means -dealloc may be called even while the notification is active. Although it's not clear this needs to be supported, this does eliminate a potential source of leaks.
    }];
        updateScore(dockTile);  // Make sure score is updated from the get-go as well
    } else {
        // Strictly speaking this may not be necessary (since the plug-in may be terminated when it's removed from the dock), but it's good practice
        [[NSDistributedNotificationCenter defaultCenter] removeObserver:self.highScoreObserver];
    self.highScoreObserver = nil;
    }
}
 
- (void)dealloc {
    if (self.highScoreObserver) {
    [[NSDistributedNotificationCenter defaultCenter] removeObserver:self.highScoreObserver];
    self.highScoreObserver = nil;
    }
    [super dealloc];
}
 
@end