On Apr 17, 2011, at 12:20 AM, WT wrote:
> On Apr 17, 2011, at 12:31 AM, Kyle Sluder wrote:
>
>>> [[[[self class] alloc] init] autorelease];
>>
>> You are in a class method. self == [self class], so no need to call +class
>> here.
>
> What if I'm trying to subclass this singleton?
What about it? 'self' identifies the actual, dynamic object receiving the
message -- in this case, a class. It is not of the static type of the
@implementation block it occurs within. Put another way, [self class] is no
more dynamic than [self alloc].
>>> + (id) allocWithZone: (NSZone*) zone;
>>> {
>>> dispatch_once(&stAllocWithZoneInvoked,
>>> ^{
>>> NSLog(@"+allocWithZone: block entered");
>>>
>>> stSharedInstance = [super allocWithZone: zone];
>>>
>>> NSLog(@"+allocWithZone: block exited");
>>> });
>>>
>>> return stSharedInstance;
>>
>> Of course this means you can't subclass this class.
>
> Why not? As long as the subclass doesn't override +allocWithZone:, this
> shouldn't be a problem, no?
How many stSharedInstance variables are there? How many stAllocWithZoneInvoked
dispatch_once predicates are there?
> About these two, once again it all came from Apple's implementation in one of
> the docs. I read it, it made sense to me at the time, so I used it often.
> Now, I wanted to replace the use of @synchronized but didn't think of
> changing anything I didn't absolutely have to change.
Apple's guide for creating singletons has, historically, been much criticized
and then subsequently much revised. If you based your implementation on that,
you might consider the criticisms as well as the revisions. One critique, as
an example: http://boredzo.org/blog/archives/2009-06-17/doing-it-wrong
Regards,
Ken
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