     
     // ButtonAreaScrollView
     private var buttonAreaScrollView = UIScrollView()
-    private var buttonAreaScrollViewHeightConstraint: NSLayoutConstraint!
+    private var buttonAreaScrollViewHeightConstraint: NSLayoutConstraint?
     private var buttonAreaHeight: CGFloat = 0.0
     
     // ButtonAreaView

            // AlertView
            let alertViewWidthConstraint = NSLayoutConstraint(item: alertView, attribute: .Width, relatedBy: .Equal, toItem: nil, attribute: .Width, multiplier: 1.0, constant: alertViewWidth)
            alertViewHeightConstraint = NSLayoutConstraint(item: alertView, attribute: .Height, relatedBy: .Equal, toItem: nil, attribute: .Height, multiplier: 1.0, constant: 1000.0)
            alertView.addConstraints([alertViewWidthConstraint, alertViewHeightConstraint])
            
        } else {
            // ContainerView

    
    // ContainerView
    private var containerView = UIView()
    private var containerViewBottomSpaceConstraint: NSLayoutConstraint?
    
    // AlertView
    public var alertView = UIView()
    public var alertViewBgColor = UIColor(red:239/255, green:240/255, blue:242/255, alpha:1.0)
    private var alertViewWidth: CGFloat = 270.0
    private var alertViewHeightConstraint: NSLayoutConstraint?
    private var alertViewPadding: CGFloat = 15.0
    private var innerContentWidth: CGFloat = 240.0
    private let actionSheetBounceHeight: CGFloat = 20.0
