[Sparkle] Singleton initalization

[Andy Matuschak]

Thanks for catching that, Christiaan. I'm a little confused about your  
code in init that checks to see if sharedUpdater is nil; that should  
never happen, since alloc gets called before init, and alloc sets the  
sharedUpdater pointer (debugger confirms).

I did actually want to restrict the singleton-ness to SUUpdater, not  
subclasses, since SUStatusChecker is a subclass of SUUpdater. That  
will probably change when I refactor SUStatusChecker, though, since  
its design isn't really very good.

Thanks for your help! http://sparkle.andymatuschak.org/changeset/118

- Andy Matuschak

On Feb 4, 2008, at 5:29 AM, Christiaan Hofman wrote:

> There is a serious bug in the current trunk. You never initialize in  
> +sharedUpdater. Also, if you'd add the init, it could easily lead to  
> excessive initialization, as you always return the shared instance  
> without checking if it was ever initialized. Moreover, you'd  
> probably always want a singleton, even when the developer wants to  
> subclass SUUpdater (the way NSDocumentController works). The design  
> could be fixed as follows.
>
>
> static id shareUpdater = nil;
>
> + (id)sharedUpdater {
> 	if (sharedUpdater == nil)
> 		[[[self class] alloc] init];
> 	return sharedUpdater;
> }
>
> - (id)allocWithZone:(NSZone *)zone {
> 	if (sharedUpdater == nil)
> 		sharedUpdater = [super allocWithZone:zone];
> 	else
> 		[sharedUpdater retain];
> 	return sharedUpdater;
> }
>
> - (id)init {
> 	if (self = [super init]) {
> 		if (sharedUpdater == nil) {
> 			[self setHostBundle:[NSBundle mainBundle]];
> 			[[NSNotificationCenter defaultCenter] addObserver:self  
> selector:@selector(applicationDidFinishLaunching:)  
> name:NSApplicationDidFinishLaunchingNotification object:NSApp];
> 		} else if (self != sharedUpdater) {
> 			// this should never happen
> 			[self release];
> 			self = [sharedUpdater retain];
> 		}
> 	}
> 	return self;
> }
>
> Instead of the extra retains of the sharedUpdater, you can also  
> override -retain, -release, -autorelease. Either one is required, or  
> your sharedUpdater may get over-released at some point.
>
> Christiaan
>