I would like to modally add a view controller with a transparent background, so the parent view controller beneath can be seen. (This is in an app for iPhone, not for iPad.)
Swift 3 -
Try vc.modalPresentationStyle = .overFullScreen
let vc = self.storyboard!.instantiateViewControllerWithIdentifier("ExampleViewController") as! ExampleViewController
vc.view.backgroundColor = UIColor.clearColor()
vc.modalPresentationStyle = .overFullScreen
self.presentViewController(vc, animated: true, completion: nil)