iOS 视图/控件旋转和复原

- (void)tnClick:(UIButton *)btn {

   [UIView animateWithDuration:0.5 animations:^{

        // 旋转  

        CGAffineTransform transform =CGAffineTransformMakeRotation(M_PI/4);

        [btn setTransform:transform];

    } completion:^(BOOL finished) {

        // 复原

        btn.transform = CGAffineTransformIdentity;

    }];

}