Attempting to load the view of a view controller while it is deallocating is not allowed and may result in undefined behavior ()

我遇見的問題即是UIAlertController事件沒加到控制器上,改為[[UIApplication sharedApplication].keyWindow.rootViewController presentViewController:alertVC animated:YES completion:nil];又遇見

'-[UIKeyboardTaskQueue waitUntilAllTasksAreFinished] may only be called from the main thread.'

再接著把這個加到主線程中,dispatch_async(dispatch_get_main_queue(), ^{

[[UIApplication sharedApplication].keyWindow.rootViewController presentViewController:alertVC animated:YES completion:nil];

解決了我的問題

});