// In a UITableViewController

import JustPeek

...

var peekController: PeekController?

// MARK: View Lifecycle

override func viewDidLoad() {
    super.viewDidLoad()
    peekController = PeekController()
    peekController?.register(viewController: self, forPeekingWithDelegate: self, sourceView: tableView)
}

// MARK: PeekingDelegate

func peekContext(_ context: PeekContext, viewControllerForPeekingAt location: CGPoint) -> UIViewController? {
    let viewController = storyboard?.instantiateViewController(withIdentifier: "ViewController")
    if let viewController = viewController, let indexPath = tableView.indexPathForRow(at: location) {
        configureViewController(viewController, withItemAtIndexPath: indexPath)
        if let cell = tableView.cellForRow(at: indexPath) {
            context.sourceRect = cell.frame
        }
        return viewController
    }
    return nil
}

func peekContext(_ context: PeekContext, commit viewController: UIViewController) {
    show(viewController, sender: self)
}