Self.revealViewController() returns nil - swift

Question

I am currently trying to get the pan gesture to reveal the controller. As of right now, my open button works, but when I add the last line, my program crashes because revealViewController is nil. Link to pod: https://github.com/John-Lluch/SWRevealViewController.
import Foundation
import UIKit
class MainViewController : UIViewController{
#IBOutlet weak var mainButton: UIView!
#IBOutlet weak var Open: UIBarButtonItem!
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated);
mainButton.makeCircle();
Open.target = self.revealViewController()
Open.action = #selector(SWRevealViewController.revealToggle(_:));
self.view.addGestureRecognizer(self.revealViewController().panGestureRecognizer());
}
}

Answer 1

It's likely you haven't set your SWRevealViewController to be the rootViewController. Remember to set Custom Class and Storyboard ID to be SWRevealViewController in your Identity inspector.
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let rootVC = storyboard.instantiateViewController(withIdentifier: "SWRevealViewController")
self.view.window?.rootViewController = rootVC
// Cont. with your code...
}
In case you need to show a login page at the beginning, you need a function in you AppDelegate, which allows the window to update the rootViewController
func changeRootVCToSWRevealVC () {
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let rootVC = storyboard.instantiateViewController(withIdentifier: "SWRevealViewController")
if let window = self.window{
window.rootViewController = rootVC
}
}
After user logged in, you can change the rooViewController to SWRevealViewController.
if let appDelegate = UIApplication.shared.delegate as? AppDelegate {
appDelegate.changeRootVCToSWRevealVC()
}
If you have a variable storing the state of the last log-in, and want to navigate directly to the Navigation Drawer menu rather than LoginViewController.
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
let rootVCId = isLoggedin ? "SWRevealViewController" : "LoginViewController"
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let rootVC = storyboard.instantiateViewController(withIdentifier: rootVCId)
self.view.window?.rootViewController = rootVC
// Cont. with your code...
}

Answer 2

I was just having this same issue and came across this post. My issue turned out to be more of an "oops!" as I missed something obvious and spent 30 minutes scratching my head on it. :facepalm:
If the accepted answer doesn't work for you, check to make sure you connected your menu property to the storyboard with an outlet.
Swift:
#IBOutlet weak var menuButton:UIBarButtonItem!
override func viewDidLoad() {
if (self.revealViewController() != nil) {
menuButton.target = self.revealViewController()
menuButton.action = #selector(SWRevealViewController.revealToggle(_:))
}
}