         let screenWidth = UIScreen.mainScreen().bounds.size.width
         var movedHeight = CGFloat(0)
         
-        if self.delegate!.respondsToSelector("photoSliderControllerWillDismiss:") {
-            self.delegate!.photoSliderControllerWillDismiss!(self)
+        if (self.delegate?.respondsToSelector("photoSliderControllerWillDismiss:") != nil) {
+            self.delegate?.photoSliderControllerWillDismiss!(self)
         }
         
         if up {

    func dissmissViewControllerAnimated(animated:Bool) {
        self.dismissViewControllerAnimated(animated, completion: { () -> Void in
            
            if self.delegate!.respondsToSelector("photoSliderControllerDidDismiss:") {
                self.delegate!.photoSliderControllerDidDismiss!(self)
            }
            
        })

    
    func closeButtonDidTap(sender:UIButton) {

        if (self.delegate?.respondsToSelector("photoSliderControllerWillDismiss:") != nil) {
            self.delegate?.photoSliderControllerWillDismiss!(self)
        }
        self.dissmissViewControllerAnimated(true)

