获取Firebase数据库值并显示ios

Question

我正在尝试从我的Firebase数据库获取用户详细信息，但是它返回一个空响应，从而仅显示定义的用户名和电子邮件。虽然我可以保存到数据库，并且所需的值可以在数据库中找到

func getU() -> Void {

    if let uid = Auth.auth().currentUser?.uid {
        print("the userid \(uid)")
        DatabaseProvider.Instance.usersRef.child(uid).observeSingleEvent(of: .value, with: { (snapshot) in

            let userData = snapshot.value as? NSDictionary
            let username = userData?["username"] as? String ?? "username"
            let email = userData?["email"] as? String ?? "email"
            let userImgUrl = userData?["profileImage"] as? String ?? ""


            self.email.text = email
            self.username.text = username
        })
    }

}