Re: Showing activity indicator during data download
Re: Showing activity indicator during data download
- Subject: Re: Showing activity indicator during data download
- From: Alastair Houghton <email@hidden>
- Date: Thu, 29 Oct 2009 16:22:30 +0000
On 29 Oct 2009, at 16:04, DKJ wrote:
On 2009-10-29, at 7:05 , Alastair Houghton wrote:
the code above is a no-no
Thanks for your reply. I'm using a UIActivityIndicatorView, and I
found a place in the docs where it says almost all of UIKit is not
thread-safe.
But just out of curiosity, what horrible things might happen with
the code I posted?
Everything from rendering faults down to outright crashes, memory
corruption and so on. It all depends on exactly what code is being
run and how it's been written.
Moreover, some of the problems may manifest themselves as
"Heisenbugs", which are notoriously difficult to track down (and in
some cases hard enough just to *understand*). Or they may only happen
on particular models, perhaps because they have a slightly faster or
slower CPU, or because they're using e.g. a different graphics driver.
Basically, all the usual problems that you might have if you start
writing multi-threaded code without paying any attention to thread-
safety.
Oh, *and* just in case you're tempted to try the "test it and use it
if it works, because it's simple" approach to software development,
you should remember that *even if* you were to test on every currently
available device and with every currently in-use version of the iPhone
OS, there's nothing stopping Apple from releasing new devices or
software updates that will cause it to break, because they didn't
guarantee thread-safety and you're assuming it.
Kind regards,
Alastair.
--
http://alastairs-place.net
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