Firebase实时数据库数据获取

我正在尝试获取以下值作为变量

但我的代码给我零

ref.child("users").child(userID!).observeSingleEvent(of: .value, with: { (snapshot) in
    // Get user value
    let value = snapshot.value as? NSDictionary
    let userInfo = value?["UserInfo"] as? NSDictionary
    let data = userInfo?["lat"] as? String ?? ""
    print(data)


    // ...
}) { (error) in
    print(error.localizedDescription)
}