Re: UITable Views and display lags
Re: UITable Views and display lags
- Subject: Re: UITable Views and display lags
- From: WT <email@hidden>
- Date: Sun, 21 Mar 2010 18:50:13 +0100
On Mar 21, 2010, at 5:52 PM, Matt Neuburg wrote:
> 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.
Why not rely on NSOperation's built-in dependency mechanism rather than write extra code to find out when loading the image(s) is done?
W.
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