iOS Swift, how to do if statement for different file extension?

I'm developping an App for IOS runnign with Swift to play some video and image in a player;

I'm calling the file for the video like:

   videoView.displayMode = GVRWidgetDisplayMode.fullscreen

and for an image:

   imageView.displayMode = GVRWidgetDisplayMode.fullscreen

I'd like to have a if statement, like;

if file being call is .png launch it via the imageViewer;

if file is mp4, launch it via the videoviewer

The code added above is being call from the super.viewDidLoad.

Any suggestions will be super !

Thanks :) :)