On Dec 1, 2013, at 07:26 , Kevin Meaney <[email protected]> wrote:
> This property is mostly changed on a queue that is not the main queue (gcd
> queues, not NSOperation queues). Everything works as I would like but I'm
> concerned that it is only working out of luck rather than proper design.
You didn’t actually state the nature of your concern. You’re worried
specifically about the problem of triggering a UI update on a background
thread? If so, then, yes, you’ve been lucky if it worked.
> Has something changed in Mavericks so that doing this is no longer a problem,
> or do I need to fix.
Nothing’s changed in Mavericks AFAIK, so you should fix your code.
> Because this is a simple case (I know when I'm not on the main thread) I can
> easily fix with just wrapping the modification of the property like so:
>
> __weak AppDelegate *weakSelf = self;
> dispatch_async(dispatch_get_main_queue(), ^
> {
> AppDelegate *strongSelf = weakSelf;
> if (strongSelf)
> strongSelf.isAgentRunning = isRunning ? @"Yes" : @"No";
> });
>
> But of course this is fine in my simple case, and since this is all I need
> I'll go with this.
Yes, but why are you taking the trouble to “avoid” a reference cycle when none
can be formed? What’s wrong with the simple version?
dispatch_async(dispatch_get_main_queue(), ^
{
self.isAgentRunning = isRunning ? @"Yes" : @"No";
});
Certainly the block captures ‘self’ in this case, but nothing other than the
queue captures the block.
> But what I suppose I'm asking is, are others using the receptionist design
> pattern, is it the way to go for a robust solution to this problem?
It’s no robuster than the “simple” solution. It’s useful when the object
modifying the property doesn’t or can’t know whether it’s a background thread —
for example, when it’s in a 3rd party library you don’t control. But in your
own code, you can always use [NSThread isMainThread] to decide whether to
update the property synchronously or asynchronously.
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