UIPopoverPresentationController on iOS 8 iPhone

You can override the default adaptive behaviour (UIModalPresentationFullScreen in compact horizontal environment, i.e. iPhone) using the
adaptivePresentationStyleForPresentationController: method available through UIPopoverPresentationController.delegate.

UIPresentationController uses this method to ask the new presentation style to use, which in your case, simply returning UIModalPresentationNone will cause the UIPopoverPresentationController to render as a popover instead of fullscreen.

Here’s an example of the popover using a segue setup in storyboard from a UIBarButtonItem to “present modally” a UIViewController

class SomeViewController: UIViewController, UIPopoverPresentationControllerDelegate {

    // override func prepareForSegue(segue: UIStoryboardSegue!, sender: AnyObject!) { // swift < 3.0
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == "PopoverSegue" {
            if let controller = segue.destinationViewController as? UIViewController {
                controller.popoverPresentationController.delegate = self
                controller.preferredContentSize = CGSize(width: 320, height: 186)                
            }
        }
    }

    // MARK: UIPopoverPresentationControllerDelegate

    //func adaptivePresentationStyleForPresentationController(controller: UIPresentationController!) -> UIModalPresentationStyle { // swift < 3.0
    func adaptivePresentationStyle(for controller: UIPresentationController) -> UIModalPresentationStyle {
        // Return no adaptive presentation style, use default presentation behaviour
        return .None
    }
}

This trick was mentioned in WWDC 2014 session 214 “View Controller Advancement in iOS8” (36:30)