UIKit

• Rotation callbacks in iOS 5 are not applied to view controllers that are presented over a full screen. What this means is that if your code presents a view controller over another view controller, and then the user subsequently rotates the device to a different orientation, upon dismissal, the underlying controller (i.e. presenting controller) will not receive any rotation callbacks. Note however that the presenting controller will receive a viewWillLayoutSubviews call when it is redisplayed, and the interfaceOrientation property can be queried from this method and used to lay out the controller correctly.
• In iOS 5, the UIPickerView class doesn't send its pickerView:didSelectRow:inComponent: delegate message in response to the programatic selection of an item.
• Returning nil from the tableView:viewForHeaderInSection: method (or its footer equivalent) is no longer sufficient to hide a header. You must override tableView:heightForHeaderInSection: and return0.0 to hide a header.
• In iOS 5, the UITableView class has two methods to move one cell from one row to another with defined parameters. These APIs are:
  • moveSection:toSection:
  • moveRowAtIndexPath:toIndexPath:
• Using the UIWebView class in Interface Builder, setting a transparent background color is possible in iOS 5. Developers compiling against the new SDK can check their XIB for the UIWebView transparent setting.
• In iOS 5, the UINavigationBar, UIToolbar, and UITabBar implementations have changed so that the drawRect: method is not called unless it is implemented in a subclass. Apps that have re-implementeddrawRect: in a category on any of these classes will find that the drawRect: method isn't called. UIKit does link-checking to keep the method from being called in apps linked before iOS 5 but does not support this design on iOS 5 or later. Apps can either:
  • Use the customization API for bars in iOS 5 and later, which is the preferred way.
  • Subclass UINavigationBar (or the other bar classes) and override drawRect: in the subclass.
• The indexPathForRow:inSection:, section, and row methods of NSIndexPath now use NSInteger instead of NSUInteger, so that these types match with methods defined on UITableView.
• The behavior of the UITableView class's scrollToRowAtIndexPath:atScrollPosition:animated: method has changed. If a scroll position of UITableViewScrollPositionTop orUITableViewScrollPositionBottom is specified, the method now adjusts for the top and bottom portions of the contentInset property.
• In releases prior to iOS 5, the UIPopoverController class would unconditionally set the autoresizing masks of view controllers that provided the content for the popover controller. It would also unconditionally set the autoresizing masks of the views of view controllers pushed on to a UINavigationController object which was the content view controller of the popover controller.The UIPopoverController class no longer does this for applications linked against iOS 5 or later. Developers should ensure that the autoresizing masks of views are set properly to allow for arbitrary resizing within any container, not just popovers. A mask of (UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight) is reasonable.
• The completion handler for saveToURL:forSaveOperation:completionHandler: is called outside of the coordinated write block.
• The autosaveWithCompletionHandler: method is now only called for period-based saves when it is safe to return without saving. Documents must save, though, if thesaveToURL:forSaveOperation:completionHandler: method is invoked.