Comments on: Queued Background Tasks for Cocoa http://blog.jayway.com/2009/05/09/queued-background-tasks-for-cocoa/ Sharing Experience Thu, 11 Mar 2010 19:33:28 +0100 http://wordpress.org/?v=2.9.2 hourly 1 By: Fredrik Olsson http://blog.jayway.com/2009/05/09/queued-background-tasks-for-cocoa/comment-page-1/#comment-15349 Fredrik Olsson Mon, 09 Nov 2009 15:55:32 +0000 http://blog.jayway.com/?p=1665#comment-15349 The reason is that all methods in UIKit should be called on the main thread. So updating the UI directly from the background task is not a good thing, sometimes it works, sometimes you crash, and sometimes just nothing happens. This is why the Apple documentation says you must always call fromt he main thread. Try to use performSelectorOnMainThread:withObject:waitUntilDone:. The reason is that all methods in UIKit should be called on the main thread. So updating the UI directly from the background task is not a good thing, sometimes it works, sometimes you crash, and sometimes just nothing happens. This is why the Apple documentation says you must always call fromt he main thread.

Try to use performSelectorOnMainThread:withObject:waitUntilDone:.

]]> By: John http://blog.jayway.com/2009/05/09/queued-background-tasks-for-cocoa/comment-page-1/#comment-15142 John Wed, 04 Nov 2009 17:29:14 +0000 http://blog.jayway.com/?p=1665#comment-15142 I'm getting the following error when using: [self performSelectorInBackgroundQueue:@selector(methodName:) withObject:nil]; bool _WebTryThreadLock(bool), 0x487aa0: Tried to obtain the web lock from a thread other than the main thread or the web thread. This may be a result of calling to UIKit from a secondary thread. Crashing now... I’m getting the following error when using:

[self performSelectorInBackgroundQueue:@selector(methodName:) withObject:nil];

bool _WebTryThreadLock(bool), 0×487aa0: Tried to obtain the web lock from a thread other than the main thread or the web thread. This may be a result of calling to UIKit from a secondary thread. Crashing now…

]]> By: Marc Love http://blog.jayway.com/2009/05/09/queued-background-tasks-for-cocoa/comment-page-1/#comment-8384 Marc Love Sat, 18 Jul 2009 04:08:56 +0000 http://blog.jayway.com/?p=1665#comment-8384 Thanks Fredrik, this is an excellent resource...especially for those of us just getting started with iPhone development and unfamiliar with such resource-constrained environments. This should be really helpful for an app I'm working on that makes heavy use of some web services. Thanks Fredrik, this is an excellent resource…especially for those of us just getting started with iPhone development and unfamiliar with such resource-constrained environments.

This should be really helpful for an app I’m working on that makes heavy use of some web services.

]]>