I get this log in the console when I am running my application in is simulator. Haven't seen this in iOS 8. I am not quite sure whats causing this. Has anyone else come across the same issue and if so how was it fixed? or is there any help anyone can provide in regards to this?
Do not change UI from anything but the main thread. While it may appear to work on some OS or devices and not others, it is bound to make your application unstable, and crash unpredictably.
If you must respond to a notification, which can happen in the background, then ensure UIKit
invocation takes place on the main thread.
You at least have these 2 options:
Use GCD
(Grand Central Dispatch) if your observer can be notified on any thread. You can listen and do work from any thread, and encapsulate UI changes in a dispatch_async
:
dispatch_async(dispatch_get_main_queue()) { // Do UI stuff here }
When to use GCD
? When you do not control who sends the notification. It can be the OS, a Cocoapod, embedded libraries, etc. Using GCD
will woke anytime, every time. Downside: You find yourself re-scheduling the work.
Conveniently, you can specify on which thread you want the observer to be notified, at the time you are registering for notifications, using the queue
parameter:
addObserverForName:@"notification" object:nil queue:[NSOperationQueue mainQueue] usingBlock:^(NSNotification *note){ // Do UI stuff here }
When to observe on main thread? When you are both registering and registered. Bu the time you respond to the notification, you are already where you need to be.
[self performSelectorOnMainThread:@selector(postNotification:) withObject:notification waitUntilDone:NO];
Hybrid solution which does not guarantee that the observer is only invoked from said method. It allows for lighter observer, at the cost less robust design. Only mentioned here as a solution you should probably avoid.
Swift 3.0
DispatchQueue.main.async { }
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