←

UISplitViewController is similar to the UINavigationController on the iPhone: it shows a master page and you can navigate to child views. However, on the iPad and suchlike the master and detail pages can be shown side-by-side.

Drag one onto your storyboard. It will create four controllers. The UISplitViewController has a "master view controller" relationship to a UINavigationController and a "detail view" relationship to a normal UIViewController. The UINavigationController has a "root view controller" relationship to a UITableViewController.

Let's create a custom class for the UITableViewController which will just show a normal table:

class SplitTableController : UITableViewController {

    override func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 5
    }

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "LabelCell", for: indexPath)
        cell.textLabel?.text = "Section \(indexPath.section) Row \(indexPath.row)"
        return cell
    }

    override func tableView(_ tableView: UITableView, titleForHeaderInSection section: Int) -> String? {
        return "Section \(section)"
    }
}

Opening the app won't do something, except show the detail view controller first, and you'll be able to back out to our table as populated above.

Let's drag a "show detail" segue, called "showDetail", from the UITableViewController to normal view controller working as our detail view. Now create a method that does something with that segue:

override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    self.performSegue(withIdentifier: "showDetail", sender: nil)
}

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "showDetail" {
        let index = self.tableView.indexPathForSelectedRow! as NSIndexPath
        let vc = segue.destination as! SplitDetailController
        vc.name = "hiya: "+String(index.row)
    }
}

This assumes you've created a custom class for our destination view controller called SplitDetailController and it has a outlet called name, which affects the view somehow. So create that now.

When you open the app now, the same will happen as before, except when you back out into the master view controller, you'll be able to click on a cell and affect, and go to, the destination view controller as above.

On the iPad, in landscape view, you'll see two panes. In iPad portrait, however, you'll only see one, and you'll have to drag from the left to pull out the table view. In the viewDidShow method in your table view controller, this will ensure it always shows both: self.splitViewController?.preferredDisplayMode = .allVisible

Finally, on the iPhone, we always go to the detail view controller first. To go to the mater view controller, our table view, first ensure the table view has the UISplitViewControllerDelegate protocol, and then override this method to say the master view controller should always collapse onto the detail view controller:

func splitViewController(_ splitViewController: UISplitViewController,
                         collapseSecondary secondaryViewController: UIViewController,
                         onto primaryViewController: UIViewController) -> Bool {
    return true
}