@IBAction func SignUpBtn_TouchUpInside(_ sender: Any) {
Auth.auth().createUser(withEmail: emailTextField.text!, password: passwordTextField.text!, completion: { (user: AuthDataResult?, error:Error?) in
if error != nil{
print(error?.localizedDescription)
return
}
let ref = Database.database().reference()
let usersRenfence = ref.child("users")
let uid = user.uid
//(HERE IS WRONG, I DONT KNOW WHAT SHOULD I DO. It's my first time study code.)
let newUserRefernce = ref.child(uid)
newUserRefernce.setValue{["username": self.usernameTextField.text!, "email": self.emailTextField.text!]
print("description: \(newUserRefernce.description())")