UIImageView is not updating

UIImageView is not updating

Hi iam using following code for loading image to uiimageview its working
when i loading that UIviewcontroller but if i open any other
uiviewcontroller from the existing one and came back to the old
uiviewcontroller and if i click a thumnail image its not not updating
UIimageview uiviewcontroller.
img contains image path (inside device) in viewdidload
[self setBookimage:img];
in setBookimage()
- (void)setBookImage:(UIImage *)bookImage{
book_cover_image.image=nil;
book_cover_image.image = bookImage;
CATransition *transition = [CATransition animation];
transition.duration = 1.0f;
transition.timingFunction = [CAMediaTimingFunction
functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
transition.type = kCATransitionFade;
[book_cover_image.layer addAnimation:transition forKey:nil];
}