SwiftでCloud Firestoreに保存したデータを取得したい

実現したいこと

SwiftにおいてCloud Firestoreに保存したデータ(userNameの値を)取得し、UILabelに反映させたい。

現状

データの保存は完了しています

データを保存した時のソースコード

Swift
1guard let uid = Auth.auth().currentUser?.uid else { return }
2                self.db.collection("User").document("(uid)").setData([
3                    "userName": Auth.auth().currentUser?.displayName! as Any,
4                    "profileImage": dowmloadURL.absoluteString,
5                    "birthday": self.birthdayTextField.text as Any
6                    ], merge: true) { (error) in
7                        if let error = error {
8                            
9                            print("Error writing document: (error)")
10                            
11                        } else {
12                            
13                            print("Document successfully written!")
14                            // 画面遷移
15                            let storyboard: UIStoryboard = self.storyboard!
16                            let viewOfAnonymousSignUp = storyboard.instantiateViewController(withIdentifier: "conformProfileView")
17                            self.navigationController?.pushViewController(viewOfAnonymousSignUp, animated: true)
18                            
19                        }
20                }

データを取得するソースコード

Swift
1
2@IBOutlet weak var userNameLabel: UILabel!
3
4func getUserInfo() {
5        
6        let db = Firestore.firestore()
7        let currentUserId = Auth.auth().currentUser?.uid
8        guard let unwrapedCurrentUserId = currentUserId else { return }
9        print(db.collection("User").whereField("userName", isEqualTo: "otaota"))
10        db.collection("User").document("(unwrapedCurrentUserId)").getDocument { (snapShot, error) in
11            if let document = snapShot {
12                
13                let dataDescription = document.data().map(String.init(describing:)) ?? "nil"
14                print(document.data() as Any)
15                print("Document data: (dataDescription)")
16                /*
17                print(document.dictionaryWithValues(forKeys: ["birthday"])
18                print(document.dictionaryWithValues(forKeys: ["profileImage"])
19                */
20                
21                userNameLabel.text =  ここにCloud Firestoreに保存されたuserNameの値を入れたい
22
23                
24            } else {
25                
26                print("Document does not exist")
27                
28            }
29        }
30        
31    }