On Mar 21, 2010, at 5:52 PM, Matt Neuburg wrote: > On Fri, 19 Mar 2010 18:55:12 +0100, WT <jrca...@gmail.com> 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. _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
