Re: UITable Views and display lags
Re: UITable Views and display lags
- Subject: Re: UITable Views and display lags
- From: Matt Neuburg <email@hidden>
- Date: Sun, 21 Mar 2010 09:52:28 -0700
- Thread-topic: UITable Views and display lags
On Fri, 19 Mar 2010 18:55:12 +0100, WT <email@hidden> said:
>On Mar 19, 2010, at 6:40 PM, Michael Davey wrote:
>
>> OK, so I have changed the code to show a placeholder image, but I am a little
uncertain as to how to fetch the images asynchronously. I could start a
background thread with performSelectorInBackground, but am concerned that this
would spawn far too many threads - does anyone have any suggestions?
>
>You might want to use an NSOperationQueue. Define NSOperation instances, each
fetching one or more images. For each fetching NSOperation you define, you
should also define a "cleanup" NSOperation, dependent on its associated fetching
one, so that when the fetching one ends, the cleanup one then swaps the
placeholder image out and the fetched images in. Make sure, though, that this
swap happens in the main thread, meaning that the cleanup NSOperation should
invoke a -performSelectorInMainThread method, rather than access the UI
directly.
I'm just curious: Why is it better to have a fetching NSOperation and a
cleanup NSOperation dependent on it, rather than a single NSOperation that
fetches and then tells the main thread to show the image? m.
--
matt neuburg, phd = email@hidden, <http://www.tidbits.com/matt/>
A fool + a tool + an autorelease pool = cool!
AppleScript: the Definitive Guide - Second Edition!
http://www.tidbits.com/matt/default.html#applescriptthings
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