what method will called when we start to rotate device and after it finished

From Apple Docs:

Sent to the view controller just before the user interface begins rotating.

- (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration

Sent to the view controller after the user interface rotates:

- (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation

See more here: UIViewController Class Reference -> Responding to View Rotation Events

ATTENTION: This is deprecated, see this post

For newcomers to this post, the methods suggested by Nekto have become deprecated in iOS 8. Apple suggests to use:

-(void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator

You can use the "size" parameter as an easy way to get whether it is transitioning to portrait or landscape.

i.e.

if (size.width > size.height)
{
    // Position elements for Landscape
}
else
{
    // Position elements for Portrait
}

More info is availablein the Docs.

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