Re: waiting for async callback in main thread
Re: waiting for async callback in main thread
- Subject: Re: waiting for async callback in main thread
- From: Dave Keck <email@hidden>
- Date: Wed, 28 Oct 2009 01:08:52 -1000
Recursive run loops always lead to cleaner but worse code (IMO, of
course :)). Recursive mouse tracking, for example, keeps all the code
dealing with the state changes in one place, and allows for
method-scope variables that keep track of the state rather than ivars.
On the other hand, you have to explicitly schedule timers and delayed
actions to perform on the mouse-tracking run loop mode, or else
they'll be delayed until the user mouses-up. I can never seem to
remember to do this, and it always leads to a that d'oh! moment.
Worse, I've found the frameworks make use of recursive run loops where
you'd least expect it, and I've never seen it documented in these
cases. This bit me in the case of NSTask's -isRunning. (And not only
does -isRunning run the run loop, but you can receive the
NSTaskDidTerminateNotification from within -isRunning's stack frame -
ouch. Guess I should file a bug about that, instead of just
complaining, eh? :))
I've hit several other brick walls from recursive run loops, but they
escape me at the moment. Nonetheless, recursive run loops are a fancy
way of blocking, and are contrary to the event-driven model that we
know and love.
I guess the rule that I stick by is "Don't use recursive run loops.
But If you do, never (ever!) run them in anything but a custom run
loop mode."
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