Swift：逆序或进度条

Question

我设法获得一个动画进度条，在10秒的时间内滚动视图的顶部。但是我需要扭转它。

以下是完整代码：

public enum BarPosition {
case Top
case TopStatus
case Bottom
}

class HBRViewController: UIViewController {

let kStandardBarHeight: CGFloat = 5

var progressBarPosition: BarPosition = BarPosition.Top
var progressBarColor: UIColor = UIColor.blueColor()

private var isProgressing: Bool = false
private var progressBar: UIView = UIView(frame: CGRectZero)

func startLoading() {
    if !isProgressing {
        self.progressBar.frame = CGRectMake(0, self.position(), 0, kStandardBarHeight)
        self.progressBar.backgroundColor = self.progressBarColor
        if self.progressBar.superview != self.view {
            self.view.addSubview(self.progressBar)
        }
        self.isProgressing = true
        let barWidth: CGFloat = self.view.frame.size.width * 1
        UIView.animateWithDuration(10, animations: { () -> Void in
            self.progressBar.frame = CGRectMake(0, self.position(), barWidth, self.kStandardBarHeight)
        })
    }
}

func finishLoading() {
    if isProgressing {
        let projectileFrame = self.progressBar.layer.presentationLayer()!.frame
        self.progressBar.layer.removeAllAnimations()
        self.progressBar.frame = projectileFrame
        UIView.animateWithDuration(0.3, animations: { () -> Void in
            self.progressBar.frame = CGRectMake(0, self.position(), self.view.frame.size.width, self.kStandardBarHeight)
        }) { (Bool) -> Void in
            self.hideProgressBar()
        }
    }
}

private func hideProgressBar() {
    UIView.animateWithDuration(0.2, animations: { () -> Void in
        switch self.progressBarPosition {
        case .Top, .TopStatus:
            self.progressBar.frame.size.height = 0
        case .Bottom:
            self.progressBar.transform = CGAffineTransformMakeTranslation(0, CGRectGetHeight(self.progressBar.frame))
        }
    }) { (Bool) -> Void in
        self.progressBar.removeFromSuperview()
        self.progressBar.transform = CGAffineTransformIdentity
        self.isProgressing = false
    }
}

func position() -> CGFloat {
    switch self.progressBarPosition {
    case .TopStatus:
        if (self.navigationController != nil) {
            return CGRectGetMaxY(self.navigationController!.navigationBar.frame)
        } else {
            return CGRectGetMaxY(UIApplication.sharedApplication().statusBarFrame)
        }
    case .Top:
        if (self.navigationController != nil) {
            return CGRectGetMaxY(self.navigationController!.navigationBar.frame)
        } else {
            return 0.0 as CGFloat
        }
    case .Bottom:
        return self.view.frame.size.height - kStandardBarHeight
    }
}

}

有人可以告诉我如何让屏幕显示在屏幕的整个宽度上然后在10秒内收缩？