下载看吧，实现很简单， Demo在这里RotatingAnimationDemo

按下按钮出发旋转，下面是实现：

- (IBAction)onButtonTouch:(id)sender
{
    // 标记翻转状态
    self.isChanged = !self.isChanged;

    // 动画配置
    NSTimeInterval duration = 0.5;
    UIViewAnimationTransition transition = self.isChanged ? UIViewAnimationTransitionFlipFromRight : UIViewAnimationTransitionFlipFromLeft;

    // 提交动画
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
    [UIView setAnimationDuration:duration];
    [UIView setAnimationTransition:transition forView:self.imageView cache:NO];
    [UIView commitAnimations];

    // 动画进行到一半，设置图片
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(duration/2.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^
    {
        self.imageView.image = [UIImage imageNamed: self.isChanged ? @"1" : @"2" ];
    });
}

晚一点给你吧