App crashes after deleting user - ios

Question

So in my app I just made it so that the user can choose to delete their account, and that works out beautifully. However after the account is deleted the app crashes. I think this is because it is trying to search for a user but it's not there.
Here is my code:
let loginController = LoginController()
func deleteAccount() {
let user = Auth.auth().currentUser
let userId = Auth.auth().currentUser?.uid
let databaseUser = Database.database().reference().child("users").child(userId!)
user?.delete { error in
if let error = error {
print(error)
} else {
self.present(self.loginController, animated: true, completion: nil)
}
}
databaseUser.removeValue(completionBlock: { (error, ref) in
if error != nil {
print(error)
} else {
self.present(self.loginController, animated: true, completion: nil)
} //Without doing this the user's account only gets deleted in the Authentication, not the whole database. I think this is the problem here?
})
}
Thank you so much in advance!

Answer 1

First you need to delete the users database as to do that you would need the let userId = Auth.auth().currentUser?.uid which is only active if the user itself is on your backend, Then you go on to delete the auth.
func deleteAccount() {
let user = Auth.auth().currentUser
let userId = Auth.auth().currentUser!.uid
let databaseUser = Database.database().reference().child("users").child(userId)
databaseUser.removeValue(completionBlock: { (error, ref) in
if error != nil {
print(error)
} else {
user?.delete { error in
if let error = error {
print(error)
} else {
self.present(self.loginController, animated: true, completion: nil)
}
}
})
}
If this still doesn't work track down the lifecycle of the user using debugging tools....

Answer 2

You are implicitly unwrapping an optional in this line with !:
let databaseUser = Database.database().reference().child("users").child(userId!)
You should check whether it's nil in the first place with a guard statement:
guard let userId = Auth.auth().currentUser?.uid else {
return
}
let databaseUser = Database.database().reference().child("users").child(userId)
[...]
Moreover, your code logic is likely to be wrong, as you are getting nil for the userId before you can work with it.

Answer 3

The code order is not ideal because deleting the user also logs them out. So the code may be trying to access the users node after the user was logged out.
Also remember that Firebase is asynchronous and the only way to know a function has completed is when the code inside the closure executes i.e. in this case the databaseUser.removeValue may be firing before the delete user or sometimes it may not.
Code is faster than the internet so it's best to leverage the closures so you know when it's safe to proceed.
Try this sequence; noting that we don't try to delete the Firebase user until we know for sure the data in the users node was deleted. There could use more error checking but you get the idea.
let userRef = self.ref.child("users").child(uid)
userRef.setValue(nil, withCompletionBlock: { snapshot in
Auth.auth().currentUser?.delete(completion: { err in
if err != nil {
print(err?.localizedDescription)
}
})
})