按下按钮时如何反转动画？

Question

如果我调用动画，如何创建一个反转动画的方法？在我的项目中，我有一个UIViewController和这个控制器的子视图，它可以完成所有的背景动画。动画的作用并不是很重要。它只是让应用程序打开时出现一些矩形：

-(void)rectBottomAnimation
{    
    NSLog(@"ANIMATION START");    

    CGRect screenBound = [[UIScreen mainScreen] bounds];
    CGSize screenSize = screenBound.size;
    CGFloat screenWidth = screenSize.width;
    CGFloat screenHeight = screenSize.height;

    for (int xcord = 0; xcord <= screenWidth; xcord += 6) {
        //BOTTOM
        [self newRectWithX:xcord y:screenHeight height:0];

        CABasicAnimation* fromBottomAnimation = [CABasicAnimation animationWithKeyPath: @"bounds"];
        fromBottomAnimation.fromValue = [NSValue valueWithCGRect: _rectangle];
        fromBottomAnimation.toValue = [NSValue valueWithCGRect:CGRectMake(xcord, 0, 7, -(screenHeight)/1.4)];
        fromBottomAnimation.duration = 0.3;
        fromBottomAnimation.fillMode = kCAFillModeForwards;
        fromBottomAnimation.removedOnCompletion = NO;

        [_myLayer addAnimation: fromBottomAnimation forKey: @"resize"];
    } 
}

所以问题是：方法看起来是什么样的，当按下按钮时会反转这个动画？