 
 // MARK: - UIView extension
 
-extension UIView
+public extension UIView
 {
     public override class func initialize() {
         struct Static {

        }
    }
    
    func xx_didMoveToSuperview() -> UIView {
        self.xx_didMoveToSuperview()
        
        self.checkAutoDisplay()


// MARK: - XXPlaceHolderConfig

public struct XXPlaceHolderConfig {
    
    public var backColor: UIColor  = UIColor.clearColor()
    public var arrowSize: CGFloat  = 3
    public var lineColor: UIColor  = UIColor.whiteColor()
    public var lineWidth: CGFloat  = 1
    public var frameColor: UIColor = UIColor.redColor()
    public var frameWidth: CGFloat = 0
    
    public var showArrow: Bool             = true
    public var showText: Bool              = true
    
    public var visible: Bool               = true
    public var autoDisplay: Bool           = false
    public var autoDisplaySystemView: Bool = false
    
    public var visibleMemberOfClasses: [AnyClass] = [AnyClass]()
    public var visibleKindOfClasses: [AnyClass]   = [AnyClass]()
    
    private let defaultMemberOfClasses: [AnyClass] = [
        UIImageView.self,
