On Fri, 19 Mar 2010 18:55:12 +0100, WT <[email protected]> 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 protected], <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 _______________________________________________ Cocoa-dev mailing list ([email protected]) 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 [email protected]
