Setting UILabels to Firestore data

I don't think my app is connected to Firestore, how would I double check this?

What code would i use to get the data of a specific data?

Code Block import UIKit
import SafariServices
import WebKit
import FirebaseFirestore
import Firebase
class TheRiddle: UIViewController {
    
    @IBOutlet weak var leading_TheRiddle: NSLayoutConstraint!
    @IBOutlet weak var trailing_TheRiddle: NSLayoutConstraint!
    
    @IBOutlet weak var CurrentRiddle: UILabel!
    @IBOutlet weak var PreviousRiddle: UILabel!
    
    var menuOut = false
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let db = Firestore.firestore()
        
        print("TheRiddle collection: ", db.collection("TheRiddle").document("Riddles"))
        
        db.collection("TheRiddle").document("Riddles").addSnapshotListener { snapshot, error in
                
            //check for error
            if error == nil {
                //check if document exists
                if snapshot != nil {
                }else {
                    if let currentRiddle = snapshot?["CurrentRiddle"] as? String {
                        self.CurrentRiddle.text = "This Weeks Riddle: " + currentRiddle
                        print(currentRiddle)
                    }
                    if let previousRiddle = snapshot?["CurrentRiddle"] as? String {
                        self.PreviousRiddle.text = "Previous Riddle: " + previousRiddle
                    }
                }
            }
            
        }
        //db.collection("test").addDocument(data: ["hi":"bye"])
    }
    
    
    @IBAction func RiddleAnswerForm(_ sender: Any) {
        let vc = SFSafariViewController(url: URL(string: "https://forms.office.com/Pages/ResponsePage.aspx?id=ytAqTDte6UK-KD5v_kOm4Y843IzqmYtFlDtLrfRYsi1UMFpUMk1GN01GS05BVFlJUElONk4yR1hKUCQlQCN0PWcu")!)
        
        present(vc, animated: true)
    }
    
    @IBAction func menuTappedTheRiddle(_ sender: Any) {
        
        if menuOut == false {
            leading_TheRiddle.constant = 150
            trailing_TheRiddle.constant = -150
            menuOut = true
        }
        else {
            leading_TheRiddle.constant = 0
            trailing_TheRiddle.constant = 0
            menuOut = false
        }
        UIView.animate(withDuration: 0.2, delay: 0.0, options: .curveEaseIn, animations: {
            self.view.layoutIfNeeded()
        }) { (animationComplete) in
            print("The animation is complete")
        }
}
}

This is the most up to date code

Code Block 
                if snapshot == nil {
                    if let currentRiddle = snapshot?["CurrentRiddle"] as? String {
                        self.CurrentRiddle.text = "This Weeks Riddle: " + currentRiddle
                        print(currentRiddle)
                    }
                    if let previousRiddle = snapshot?["CurrentRiddle"] as? String {
                        self.PreviousRiddle.text = "Previous Riddle: " + previousRiddle
                    }
                }

Code Block 
                if let snapshot = snapshot {
                    if let currentRiddle = snapshot["CurrentRiddle"] as? String {
                        self.CurrentRiddle.text = "This Weeks Riddle: " + currentRiddle
                        print(currentRiddle)
                    }
                    if let previousRiddle = snapshot["CurrentRiddle"] as? String {
                        self.PreviousRiddle.text = "Previous Riddle: " + previousRiddle
                    }
                }

as you can see it says not nil

”!=“ is not, right? Thats what I have learned. 

Code Block 
                if snapshot != nil {
                    //# Doing nothing when `snapshot` is *not nil*
                }else {
                    //# This code block is executed when `snapshot` *is nil*
                    //...
                }

Code Block 
                if snapshot == nil {
                    //# This code block is executed when `snapshot` *is nil*
                    //...
                }

However it is working now and I am very grateful!